Authority: 40 U.S.C. 3704; 29 U.S.C. 653, 655, 657; Secretary of Labor's Order No. 12-71 (36 FR 8754), 8-76 (41 FR 25059), 9-83 (48 FR 35736), 1-90 (55 FR 9033), 6-96 (62 FR 111), 3-2000 (65 FR 50017), 5-2002 (67 FR 65008), 5-2007 (72 FR 31160), 4-2010 (75 FR 55355), or 1-2012 (77 FR 3912); 29 CFR part 1911; and 5 U.S.C. 553, as applicable.

Section 1926.61 also issued under 49 U.S.C. 5101 et seq.

Section 1926.62 also issued under 42 U.S.C. 4853

Section 1926.65 also issued under 126 of Public Law 99-499, 100 Stat. 1613.

[55 FR 50687, Dec. 10, 1990; 57 FR 49272, Oct. 30, 1992; 58 FR 26627, May 4, 1993; 58 FR 34218, June 24, 1993; 58 FR 35310, June 30, 1993; 59 FR 6170, Feb. 9, 1994; 59 FR 17479, April 13, 1994; 59 FR 36695, July 19, 1994; 59 FR 43268, Aug. 22, 1994; 59 FR 65947, Dec. 22, 1994; 61 FR 9227, March 7, 1996; 61 FR 31427, June 20, 1996; 62 FR 1493, Jan. 10, 1997; 63 FR 1152, Jan. 8, 1998; 63 FR 33450, June 18, 1998; 70 FR 1143, Jan. 5, 2005; 71 FR 16674, April 3, 2006; 71 FR 50191, August 24, 2006; 73 FR 75588, Dec. 12, 2008; 76 FR 33611, June 8, 2011; 76 FR 80740, Dec. 27, 2011; 77 FR 17889, March 26, 2012; 78 FR 9315, Feb. 8, 2013; 81 FR 16875, March 25, 2016; 81 FR 60273, September 1, 2016; 82 FR 2750, Jan. 9, 2017]
The employer shall ensure the availability of medical personnel for advice and consultation on matters of occupational health.
Provisions shall be made prior to commencement of the project for prompt medical attention in case of serious injury.
In the absence of an infirmary, clinic, hospital, or physician, that is reasonably accessible in terms of time and distance to the worksite, which is available for the treatment of injured employees, a person who has a valid certificate in first-aid training from the U.S. Bureau of Mines, the American Red Cross, or equivalent training that can be verified by documentary evidence, shall be available at the worksite to render first aid.
First aid supplies shall be easily accessible when required.
The contents of the first aid kit shall be placed in a weatherproof container with individual sealed packages for each type of item, and shall be checked by the employer before being sent out on each job and at least weekly on each job to ensure that the expended items are replaced.
Proper equipment for prompt transportation of the injured person to a physician or hospital, or a communication system for contacting necessary ambulance service, shall be provided.
In areas where 911 is not available, the telephone numbers of the physicians, hospitals, or ambulances shall be conspicuously posted.
Where the eyes or body of any person may be exposed to injurious corrosive materials, suitable facilities for quick drenching or flushing of the eyes and body shall be provided within the work area for immediate emergency use.

[44 FR 8577, Feb. 9, 1979; 44 FR 20940, Apr. 6, 1979, as amended at 49 FR 18295, Apr. 30, 1984; 58 FR 35084, June 30, 1993; 61 FR 5507, Feb. 13, 1996; 63 FR 33450, June 18, 1998]
Appendix A to § 1926.50 -- First aid Kits (Non-Mandatory)

First aid supplies are required to be easily accessible under paragraph Sec. 1926.50(d)(1). An example of the minimal contents of a generic first aid kit is described in American National Standard (ANSI) Z308.1-1978 "Minimum Requirements for Industrial Unit-Type First-aid Kits". The contents of the kit listed in the ANSI standard should be adequate for small work sites. When larger operations or multiple operations are being conducted at the same location, employers should determine the need for additional first aid kits at the worksite, additional types of first aid equipment and supplies and additional quantities and types of supplies and equipment in the first aid kits.

In a similar fashion, employers who have unique or changing first-aid needs in their workplace may need to enhance their first-aid kits. The employer can use the OSHA 300 log, OSHA 301 log, or other reports to identify these unique problems. Consultation from the local fire/rescue department, appropriate medical professional, or local emergency room may be helpful to employers in these circumstances. By assessing the specific needs of their workplace, employers can ensure that reasonably anticipated supplies are available. Employers should assess the specific needs of their worksite periodically and augment the first aid kit appropriately.

If it is reasonably anticipated employees will be exposed to blood or other potentially infectious materials while using first-aid supplies, employers should provide personal protective equipment (PPE). Appropriate PPE includes gloves, gowns, face shields, masks and eye protection (see "Occupational Exposure to Blood borne Pathogens", 29 CFR 1910.1030(d)(3)) (56 FR 64175).

[63 FR 33450, June 18, 1998; 76 FR 80740, Dec. 27, 2011]
An adequate supply of potable water shall be provided in all places of employment.
Portable containers used to dispense drinking water shall be capable of being tightly closed, and equipped with a tap. Water shall not be dipped from containers.
Any container used to distribute drinking water shall be clearly marked as to the nature of its contents and not used for any other purpose.
The common drinking cup is prohibited.
Where single service cups (to be used but once) are supplied, both a sanitary container for the unused cups and a receptacle for disposing of the used cups shall be provided.
Potable water means water that meets the standards for drinking purposes of the State or local authority having jurisdiction, or water that meets the quality standards prescribed by the U.S. Environmental Protection Agency's National Primary Drinking Water Regulations (40 CFR part 141).
Outlets for nonpotable water, such as water for industrial or firefighting purposes only, shall be identified by signs meeting the requirements of Subpart G of this part, to indicate clearly that the water is unsafe and is not to be used for drinking, washing, or cooking purposes.
There shall be no cross-connection, open or potential, between a system furnishing potable water and a system furnishing nonpotable water.
Toilets shall be provided for employees according to the following table:

Table D-1
Number of
Minimum number of facilities
20 or less 1
20 or more 1 toilet seat and 1 urinal per 40 workers.
200 or more 1 toilet seat and 1 urinal per 50 workers.
Under temporary field conditions, provisions shall be made to assure not less than one toilet facility is available.
Job sites, not provided with a sanitary sewer, shall be provided with one of the following toilet facilities unless prohibited by local codes:
Privies (where their use will not contaminate ground or surface water);
Recirculating toilets;
Combustion toilets.
Chemical toilets;
The requirements of this paragraph (c) for sanitation facilities shall not apply to mobile crews having transportation readily available to nearby toilet facilities.
All employees' food service facilities and operations shall meet the applicable laws, ordinances, and regulations of the jurisdictions in which they are located.
All employee food service facilities and operations shall be carried out in accordance with sound hygienic principles. In all places of employment where all or part of the food service is provided, the food dispensed shall be wholesome, free from spoilage, and shall be processed, prepared, handled, and stored in such a manner as to be protected against contamination.
When temporary sleeping quarters are provided, they shall be heated, ventilated, and lighted.
The employer shall provide adequate washing facilities for employees engaged in the application of paints, coating, herbicides, or insecticides, or in other operations where contaminants may be harmful to the employees. Such facilities shall be in near proximity to the worksite and shall be so equipped as to enable employees to remove such substances.
Washing facilities shall be maintained in a sanitary condition.
Lavatories shall be made available in all places of employment. The requirements of this subdivision do not apply to mobile crews or to normally unattended work locations if employees working at these locations have transportation readily available to nearby washing facilities which meet the other requirements of this paragraph.
Hand soap or similar cleansing agents shall be provided.
Individual hand towels or sections thereof, of cloth or paper, air blowers or clean individual sections of continuous cloth toweling, convenient to the lavatories, shall be provided.
Each lavatory shall be provided with hot and cold running water, or tepid running water.
Whenever showers are required by a particular standard, the showers shall be provided in accordance with paragraphs (f)(4)(ii) through (v) of this section.
Body soap or other appropriate cleansing agents convenient to the showers shall be provided as specified in paragraph (f)(3)(iii) of this section.
Showers shall be provided with hot and cold water feeding a common discharge line.
Employees who use showers shall be provided with individual clean towels.
One shower shall be provided for each 10 employees of each sex, or numerical fraction thereof, who are required to shower during the same shift.
No employee shall be allowed to consume food or beverages in a toilet room nor in any area exposed to a toxic material.
Every enclosed workplace shall be so constructed, equipped, and maintained, so far as reasonably practicable, as to prevent the entrance or harborage of rodents, insects, and other vermin. A continuing and effective extermination program shall be instituted where their presence is detected.
Whenever employees are required by a particular standard to wear protective clothing because of the possibility of contamination with toxic materials, change rooms equipped with storage facilities for street clothes and separate storage facilities for the protective clothing shall be provided.

[44 FR 8577, Feb. 9, 1979; 44 FR 20940, Apr. 6, 1979, as amended at 58 FR 35084; June 30, 1993; 76 FR 33611, June 8, 2011]
Protection against the effects of noise exposure shall be provided when the sound levels exceed those shown in Table D-2 of this section when measured on the A-scale of a standard sound level meter at slow response.
When employees are subjected to sound levels exceeding those listed in Table D-2 of this section, feasible administrative or engineering controls shall be utilized. If such controls fail to reduce sound levels within the levels of the table, personal protective equipment as required in Subpart E, shall be provided and used to reduce sound levels within the levels of the table.
If the variations in noise level involve maxima at intervals of 1 second or less, it is to be considered continuous.
In all cases where the sound levels exceed the values shown herein, a continuing, effective hearing conservation program shall be administered.

Duration per day,
Sound level dBA
slow response
8 90
6 92
4 95
3 97
2 100
11/2 102
1 105
1/2 110
1/4 or less 115
When the daily noise exposure is composed of two or more periods of noise exposure of different levels, their combined effect should be considered, rather than the individual effect of each. Exposure to different levels for various periods of time shall be computed according to the formula set forth in paragraph (d)(2)(ii) of this section.
A sample computation showing an application of the formula in paragraph (d)(2)(ii) of this section is as follows. An employee is exposed at these levels for these periods:

110 db A 1/4 hour.
100 db A 1/2 hour.
90 db A 11/2 hours.

Fe = (1/4 divided by 1/2)+(1/2 divided by 2)+(11/2 divided by 8)
Fe = 0.500+0.25+0.188
Fe = 0.938

Since the value of Fe does not exceed unity, the exposure is within permissible limits.
Fe = (T1/L1) (T2/L2) • • • (Tn/Ln)

Fe = The equivalent noise exposure factor.
T = The period of noise exposure at any essentially constant level.
L = The duration of the permissible noise exposure at the constant level (from Table D-2).

If the value of Fe exceeds unity (1) the exposure exceeds permissible levels.
Exposure to impulsive or impact noise should not exceed 140 dB peak sound pressure level.
In construction and related activities involving the use of sources of ionizing radiation, the pertinent provisions of the Nuclear Regulatory Commission Standards for Protection Against Radiation (10 CFR Part 20), relating to protection against occupational radiation exposure, shall apply.
Any activity which involves the use of radioactive materials or X-rays, whether or not under license from the Nuclear Regulatory Commission, shall be performed by competent persons specially trained in the proper and safe operation of such equipment. In the case of materials used under Commission license, only persons actually licensed, or competent persons under direction and supervision of the licensee, shall perform such work.

Note: The requirements applicable to construction work under paragraphs (c) through (r) of this section are identical to those set forth at paragraphs (a) through (p) of 1910.1096 of this chapter.

[44 FR 8577, Feb. 9, 1979; 44 FR 20940, Apr. 6, 1979, as amended at 58 FR 35084 & 35310; June 30, 1993; 61 FR 5507, Feb. 13, 1996; 61 FR 31427, June 20, 1996]
Only qualified and trained employees shall be assigned to install, adjust, and operate laser equipment.
Proof of qualification of the laser equipment operator shall be available and in possession of the operator at all times.
Employees, when working in areas in which a potential exposure to direct or reflected laser light greater than 0.005 watts (5 milliwatts) exists, shall be provided with antilaser eye protection devices as specified in Subpart E of this part.
Areas in which lasers are used shall be posted with standard laser warning placards.
Beam shutters or caps shall be utilized, or the laser turned off, when laser transmission is not actually required. When the laser is left unattended for a substantial period of time, such as during lunch hour, overnight, or at change of shifts, the laser shall be turned off.
Only mechanical or electronic means shall be used as a detector for guiding the internal alignment of the laser.
The laser beam shall not be directed at employees.
When it is raining or snowing, or when there is dust or fog in the air, the operation of laser systems shall be prohibited where practicable; in any event, employees shall be kept out of range of the area of source and target during such weather conditions.
Laser equipment shall bear a label to indicate maximum output.
Employees shall not be exposed to light intensities above:
Direct staring: 1 micro-watt per square centimeter;
Incidental observing: 1 milliwatt per square centimeter;
Diffused reflected light: 2 1/2 watts per square centimeter.
Laser unit in operation should be set up above the heads of the employees, when possible.
Employees shall not be exposed to microwave power densities in excess of 10 milliwatts per square centimeter.
Exposure of employees to inhalation, ingestion, skin absorption, or contact with any material or substance at a concentration above those specified in the "Threshold Limit Values of Airborne Contaminants for 1970" of the American Conference of Governmental Industrial Hygienists, shall be avoided. See appendix A to this section.
To achieve compliance with paragraph (a) of this section, administrative or engineering controls must first be implemented whenever feasible. When such controls are not feasible to achieve full compliance, protective equipment or other protective measures shall be used to keep the exposure of employees to air contaminants within the limits prescribed in this section. Any equipment and technical measures used for this purpose must first be approved for each particular use by a competent industrial hygienist or other technically qualified person. Whenever respirators are used, their use shall comply with §1926.103.
Paragraphs (a) and (b) of this section do not apply to the exposure of employees to airborne asbestos, tremolite, anthophyllite, or actinolite dust. Whenever any employee is exposed to airborne asbestos, tremolite, anthophyllite, or actinolite dust, the requirements of §1910.1101 or §1926.58 of this title shall apply.
Paragraphs (a) and (b) of this section do not apply to the exposure of employees to formaldehyde. Whenever any employee is exposed to formaldehyde, the requirements of §1910.1048 of this title shall apply.

[39 FR 22801, June 24, 1974, as amended at 51 FR 37007, Oct. 17, 1986; 52 FR 46312, Dec. 4, 1987; 58 FR 35089; June 30, 1993]
Appendix A to § 1926.55—1970 American Conference of Governmental Industrial Hygienists' Threshold Limit Values of Airborne Contaminants

Threshold Limit Values of Airborne Contaminants for Construction
Substance CAS No.d ppma* mg/m3b Skin Designation
Abate; see Temephos
Acetaldehyde 75-07-0 200 360 -
Acetic acid 64-19-7 10 25 -
Acetic anhydride 108-24-7 5 20 -
Acetone 67-64-1 1000 2400 -
Acetonitrile 75-05-8 40 70 -
2-Acetylaminofluorine; see §1926.1114 53-96-3
Acetylene 74-86-2 E
Acetylene dichloride; see 1,2-Dichloroethylene
Acetylene tetrabromide 79-27-6 1 14 -
Acrolein 107-02-8 0.1 0.25 -
Acrylamide 79-06-1 - 0.3 X
Acrylonitrile; see §1926.1145 107-13-1
Aldrin 309-00-2 - 0.25 X
Allyl alcohol 107-18-6 2 5 X
Allyl chloride 107-05-1 1 3 -
Allyl glycidyl ether (AGE) 106-92-3 (C)10 (C)45 -
Allyl propyl disulfide 2179-59-1 2 12 -
alpha-Alumina 1344-28-1
Total dust - -
Respirable fraction - -
Alundum; see alpha-Alumina
4-Aminodiphenyl; see §1926.1111 92-67-1
2-Aminoethanol; see Ethanolamine
2-Aminopyridine 504-29-0 0.5 2 -
Ammonia 7664-41-7 50 35 -
Ammonium sulfamate 7773-06-0
Total dust - 15 -
Respirable fraction - 5 -
n-Amyl acetate 628-63-7 100 525 -
sec-Amyl acetate 626-38-0 125 650 -
Aniline and homologs 62-53-3 5 19 X
Anisidine (o-, p-isomers) 29191-52-4 - 0.5 X
Antimony and compounds (as Sb) 7440-36-0 - 0.5 -
ANTU (alpha Naphthylthiourea) 86-88-4 - 0.3 -
Argon 7440-37-1 E
Arsenic, inorganic compounds (as As); see §1926.1118 7440-38-2 - - -
Arsenic, organic compounds (as As) 7440-38-2 - 0.5 -
Arsine 7784-42-1 0.05 0.2 -
Asbestos; see 1926.58
Azinphos-methyl 86-50-0 - 0.2 X
Barium, soluble compounds (as Ba) 7440-39-3 - 0.5 -
Benzeneg; see §1926.1128 71-43-2
Benzidine; see §1926.1110 92-87-5
p-Benzoquinone; see Quinone
Benzo(a)pyrene; see Coal tar pitch volatiles
Benzoyl peroxide 94-36-0 - 5 -
Benzyl chloride 100-44-7 1 5 -
Beryllium and beryllium compounds (as Be); see 1926.1124 (q) 7440-41-7 - 0.002 -
Biphenyl; see Diphenyl
Bisphenol A; see Diglycidyl ether
Boron oxide 1303-86-2
Total dust - 15 -
Boron tribromide 10294-33-4 1 10 -
Boron trifluoride 7637-07-2 (C)1 (C)3 -
Bromine 7726-95-6 0.1 0.7 -
Bromine pentafluoride 7789-30-2 0.1 0.7 -
Bromoform 75-25-2 0.5 5 X
Butadiene (1,3-Butadiene); see 29 CFR 1910.1051; 29 CFR 1910.19(l) 106-99-0 STEL 1 ppm/5 ppm -
Butanethiol; see Butyl mercaptan
2-Butanone (Methyl ethyl ketone) 78-93-3 200 590 -
2-Butoxyethanol 111-76-2 50 240 X
n-Butyl-acetate 123-86-4 150 710 -
sec-Butyl acetate 105-46-4 200 950 -
tert-Butyl acetate 540-88-5 200 950 -
n-Butyl alcohol 71-36-3 100 300 -
sec-Butyl alcohol 78-92-2 150 450 -
tert-Butyl alcohol 75-65-0 100 300 -
Butylamine 109-73-9 (C)5 (C)15 X
tert-Butyl chromate (as CrO3); see 1926.1126n 1189-85-1
n-Butyl glycidyl ether (BGE) 2426-08-6 50 270 -
Butyl mercaptan 109-79-5 0.5 1.5 -
p-tert-Butyltoluene 98-51-1 10 60 -
Cadmium (as Cd); see 1926.1127 7440-43-9
Calcium carbonate 1317-65-3
Total dust - -
Respirable fraction - -
Calcium oxide 1305-78-8 - 5 -
Calcium sulfate 7778-18-9
Total dust - 15 -
Respirable fraction - 5 -
Camphor, synthetic 76-22-2 - 2 -
Carbaryl (Sevin) 63-25-2 - 5 -
Carbon black 1333-86-4 - 3.5 -
Carbon dioxide 124-38-9 5000 9000 -
Carbon disulfide 75-15-0 20 60 X
Carbon monoxide 630-08-0 50 55 -
Carbon tetrachloride 56-23-5 10 65 X
Cellulose 9004-34-6
Total dust - -
Respirable fraction - -
Chlordane 57-74-9 - 0.5 X
Chlorinated camphene 8001-35-2 - 0.5 X
Chlorinated diphenyl oxide 55720-99-5 - 0.5 -
Chlorine 7782-50-5 1 3 -
Chlorine dioxide 10049-04-4 0.1 0.3
Chlorine trifluoride 7790-91-2 (C)0.1 (C)0.4 -
Chloroacetaldehyde 107-20-0 (C)1 (C)3 -
a-Chloroacetophenone (Phenacyl chloride) 532-27-4 0.05 0.3 -
Chlorobenzene 108-90-7 75 350 -
o-Chlorobenzylidene malononitrile 2698-41-1 0.05 0.4 -
Chlorobromomethane 74-97-5 200 1050 -
2-Chloro-1,3-butadiene; see beta-Chloroprene
Chlorodiphenyl (42% Chlorine) (PCB) 53469-21-9 - 1 X
Chlorodiphenyl (54% Chlorine) (PCB) 11097-69-1 - 0.5 X
1-Chloro,2,3-epoxypropane; see Epichlorohydrin
2-Chloroethanol; see Ethylene chlorohydrin
Chloroethylene; see Vinyl chloride
Chloroform (Trichloromethane) 67-66-3 (C)50 (C)240 -
bis(Chloromethyl) ether; see §1926.1108 542-88-1
Chloromethyl methyl ether; see §1926.1106 107-30-2
1-Chloro-1-nitropropane 600-25-9 20 100 -
Chloropicrin 76-06-2 0.1 0.7 -
beta-Chloroprene 126-99-8 25 90 X
Chromium (II) compounds
(as Cr) 7440-47-3 - 0.5 -
Chromium (III) compounds
(as Cr) 7440-47-3 - 0.5 -
Chromium (VI) compounds; See 1926.1126o
Chromium metal and insol. salts (as Cr) 7440-47-3 - 1 -
Chrysene; see Coal tar pitch volatiles
Coal tar pitch volatiles (benzene soluble fraction), anthracene, BaP, phenanthrene, acridine, chrysene, pyrene 65996-93-2 - 0.2 -
Cobalt metal, dust, and fume (as Co) 7440-48-4 - 0.1 -
Coke oven emissions; see §1926.1129
Copper 7440-50-8
Fume (as Cu) - 0.1 -
Dusts and mists (as Cu) - 1 -
Corundum; see Emery
Cotton dust (raw) - 1
Crag herbicide (Sesone) 136-78-7
Total dust - -
Respirable fraction - -
Cresol, all isomers 1319-77-3 5 22 X
Crotonaldehyde 123-73-9; 2 6
Cumene 98-82-8 50 245 X
Cyanides (as CN) Varies with Compound - 5 X
Cyanogen 460-19-5 10 - -
Cyclohexane 110-82-7 300 1050 -
Cyclohexanol 108-93-0 50 200 -
Cyclohexanone 108-94-1 50 200 -
Cyclohexene 110-83-8 300 1015 -
Cyclonite 121-82-4 - 1.5 X
Cyclopentadiene 542-92-7 75 200 -
DDT, see Dichlorodiphenyltrichloroethane
DDVP, see Dichlorvos
2,4-D (Dichlorophenoxyacetic acid) 94-75-7 - 10 -
Decaborane 17702-41-9 0.05 0.3 X
Demeton (Systox) 8065-48-3 - 0.1 X
Diacetone alcohol (4-Hydroxy-4-methyl-2-pentanone) 123-42-2 50 240 -
1,2-Diaminoethane; see Ethylenediamine
Diazomethane 334-88-3 0.2 0.4 -
Diborane 19287-45-7 0.1 0.1 -
1,2-Dibromo-3-chloropropane (DBCP); see §1926.1144 96-12-8 -
1,2-Dibromoethane; see Ethylene dibromide
Dibutyl phosphate 107-66-4 1 5 -
Dibutyl phthalate 84-74-2 - 5 -
Dichloroacetylene 7572-29-4 (C)0.1 (C)0.4 -
o-Dichlorobenzene 95-50-1 (C)50 (C)300 -
p-Dichlorobenzene 106-46-7 75 450 -
3,3'-Dichlorobenzidine; see §1926.1107 91-94-1
Dichlorodifluoromethane 75-71-8 1000 4950 -
1,3-Dichloro-5,5-dimethyl hydantoin 118-52-5 - 0.2 -
Dichlorodiphenyltrichloroethane (DDT) 50-29-3 - 1 X
1,1-Dichloroethane 75-34-3 100 400 -
1,2-Dichloroethane; see Ethylene dichloride
1,2-Dichloroethylene 540-59-0 200 790 -
Dichloroethyl ether 111-44-4 (C)15 (C)90 X
Dichloromethane; see Methylene chloride
Dichloromonofluoromethane 75-43-4 1000 4200 -
1,1-Dichloro-1-nitroethane 594-72-9 (C)10 (C)60 -
1,2-Dichloropropane; see Propylene dichloride
Dichlorotetrafluoroethane 76-14-2 1000 7000 -
Dichlorvos (DDVP) 62-73-7 - 1 X
Dieldrin 60-57-1 - 0.25 X
Diethylamine 109-89-7 25 75 -
2-Diethylaminoethanol 100-37-8 10 50 X
Diethylene triamine 111-40-0 (C)10 (C)42 X
Diethyl ether; see Ethyl ether
Difluorodibromomethane 75-61-6 100 860 -
Diglycidyl ether (DGE) 2238-07-5 (C)0.5 (C)2.8 -
Dihydroxybenzene; see Hydroquinone
Diisobutyl ketone 108-83-8 50 290 -
Diisopropylamine 108-18-9 5 20 X
4-Dimethylaminoazobenzene; see §1926.1115 60-11-7
Dimethoxymethane; see Methylal
Dimethyl acetamide 127-19-5 10 35 X
Dimethylamine 124-40-3 10 18 -
Dimethylaminobenzene; see Xylidine
Dimethylaniline (N,N-Dimethylaniline) 121-69-7 5 25 X
Dimethylbenzene; see Xylene
Dimethyl-1,2-dibromo- 2,2-dichloroethyl phosphate 300-76-5 - 3 -
Dimethylformamide 68-12-2 10 30 X
2,6-Dimethyl-4-heptanone; see Diisobutyl ketone
1,1-Dimethylhydrazine 57-14-7 0.5 1 X
Dimethylphthalate 131-11-3 - 5 -
Dimethyl sulfate 77-78-3 1 5 X
Dinitrobenzene (all isomers) 1 X
(ortho) 528-29-0
(meta) 99-65-0
(para) 100-25-4
Dinitro-o-cresol 534-52-1 - 0.2 X
Dinitrotoluene 25321-14-6 - 1.5 X
Dioxane (Diethylene dioxide) 123-91-1 100 360 X
Diphenyl (Biphenyl) 92-52-4 0.2 1 -
Diphenylamine 122-39-4 - 10 -
Diphenylmethane diisocyanate; see Methylene bisphenyl isocyanate
Dipropylene glycol methyl ether 34590-94-8 100 600 X
Di-sec octyl phthalate (Di-(2-ethylhexyl) phthalate) 117-81-7 - 5 -
Emery 12415-34-8
Total dust - -
Respirable fraction - -
Endosulfan 115-29-7 - 0.1 X
Endrin 72-20-8 - 0.1 X
Epichlorohydrin 106-89-8 5 19 X
EPN 2104-64-5 - 0.5 X
1,2-Epoxypropane; see Propylene oxide
2,3-Epoxy-1-propanol; see Glycidol
Ethane 74-84-0 E
Ethanethiol; see Ethyl mercaptan
Ethanolamine 141-43-5 3 6 -
2-Ethoxyethanol (Cellosolve) 110-80-5 200 740 X
2-Ethoxyethyl acetate (Cellosolve acetate) 111-15-9 100 540 X
Ethyl acetate 141-78-6 400 1400 -
Ethyl acrylate 140-88-5 25 100 X
Ethyl alcohol (Ethanol) 64-17-5 1000 1900 -
Ethylamine 75-04-7 10 18 -
Ethyl amyl ketone (5-Methyl-3-heptanone) 541-85-5 25 130 -
Ethyl benzene 100-41-4 100 435 -
Ethyl bromide 74-96-4 200 890 -
Ethyl butyl ketone (3-Heptanone) 106-35-4 50 230 -
Ethyl chloride 75-00-3 1000 2600 -
Ethyl ether 60-29-7 400 1200 -
Ethyl formate 109-94-4 100 300 -
Ethyl mercaptan 75-08-1 0.5 1 -
Ethyl silicate 78-10-4 100 850 -
Ethylene 74-85-1 E
Ethylene chlorohydrin 107-07-3 5 16 X
Ethylenediamine 107-15-3 10 25 -
Ethylene dibromide 106-93-4 (C)25 (C)190 X
Ethylene dichloride (1,2-Dichloroethane) 107-06-2 50 200 -
Ethylene glycol dinitrate 628-96-6 (C)0.2 (C)1 X
Ethylene glycol methyl acetate; see Methyl cellosolve acetate
Ethyleneimine; see §1926.1112 151-56-4
Ethylene oxide; see §1926.1147 75-21-8
Ethylidene chloride; see 1,1-Dichloroethane
N-Ethylmorpholine 100-74-3 20 94 X
Ferbam 14484-64-1
Total dust - 15 -
Ferrovanadium dust 12604-58-9 - 1 -
Fibrous Glass
Total dust -
Respirable fraction - -
Fluorides (as F) Varies with compound - 2.5 -
Fluorine 7782-41-4 0.1 0.2 -
Fluorotrichloromethane (Trichlorofluoromethane) 75-69-4 1000 5600 -
Formaldehyde; see §1926.1148 50-00-0
Formic acid 64-18-6 5 9 -
Furfural 98-01-1 5 20 X
Furfuryl alcohol 98-00-0 50 200 -
Gasoline 8006-61-9 A3 -
Glycerin (mist) 56-81-5
Total dust - -
Respirable fraction - -
Glycidol 556-52-5 50 150 -
Glycol monoethyl ether; see 2-Ethoxyethanol
Graphite, natural, respirable dust 7782-42-5 (2) (2) (2)
Graphite, synthetic
Total dust - -
Respirable fraction - -
Guthion; see Azinphos methyl
Gypsum 13397-24-5
Total dust - -
Respirable fraction - -
Hafnium 7440-58-6 - 0.5 -
Helium 7440-59-7 E
Heptachlor 76-44-8 - 0.5 X
Heptane (n-Heptane) 142-82-5 500 2000 -
Hexachloroethane 67-72-1 1 10 X
Hexachloronaphthalene 1335-87-1 - 0.2 X
n-Hexane 110-54-3 500 1800 -
2-Hexanone (Methyl n-butyl ketone) 591-78-6 100 410 -
Hexone (Methyl isobutyl ketone) 108-10-1 100 410 -
sec-Hexyl acetate 108-84-9 50 300 -
Hydrazine 302-01-2 1 1.3 X
Hydrogen 1333-74-0 E
Hydrogen bromide 10035-10-6 3 10 -
Hydrogen chloride 7647-01-0 (C)5 (C)7 -
Hydrogen cyanide 74-90-8 10 11 X
Hydrogen fluoride (as F) 7664-39-3 3 2 -
Hydrogen peroxide 7722-84-1 1 1.4 -
Hydrogen selenide (as Se) 7783-07-5 0.05 .02 -
Hydrogen sulfide 7783-06-4 10 15 -
Hydroquinone 123-31-9 - 2 -
Indene 95-13-6 10 45 -
Indium and compounds (as In) 7440-74-6 - 0.1 -
Iodine 7553-56-2 (C)0.1 (C)1 -
Iron oxide fume 1309-37-1 - 10 -
Iron salts (soluble) (as Fe) Varies with compound - 1 -
Isoamyl acetate 123-92-2 100 525 -
Isoamyl alcohol (primary and secondary) 123-51-3 100 360 -
Isobutyl acetate 110-19-0 150 700 -
Isobutyl alcohol 78-83-1 100 300 -
Isophorone 78-59-1 25 140 -
Isopropyl acetate 108-21-4 250 950 -
Isopropyl alcohol 67-63-0 400 980 -
Isopropylamine 75-31-0 5 12 -
Isopropyl ether 108-20-3 500 2100 -
Isopropyl glycidyl ether (IGE) 4016-14-2 50 240 -
Kaolin 1332-58-7
Total dust - -
Respirable fraction - -
Ketene 463-51-4 0.5 0.9 -
Lead, inorganic (as Pb); see 1926.62 7439-92-1
Limestone 1317-65-3
Total dust - -
Respirable fraction - -
Lindane 58-89-9 - 0.5 X
Lithium hydride 7580-67-8 - 0.025 -
L.P.G. (Liquefied petroleum gas) 68476-85-7 1000 1800
Magnesite 546-93-0
Total dust - -
Respirable fraction - -
Magnesium oxide fume 1309-48-4
Total particulate 15 - -
Malathion 121-75-5
Total dust - 15 X
Maleic anhydride 108-31-6 0.25
Manganese compounds (as Mn) 7439-96-5 - (C)5 -
Manganese fume (as Mn) 7439-96-5 - (C)5 -
Marble 1317-65-3
Total dust - -
Respirable fraction - -
Mercury (aryl and inorganic)(as Hg) 7439-97-6 0.1 X
Mercury (organo) alkyl compounds (as Hg) 7439-97-6 - 0.01 X
Mercury (vapor) (as Hg) 7439-97-6 - 0.1 X
Mesityl oxide 141-79-7 25 100 -
Methane 74-82-8 E
Methanethiol; see Methyl mercaptan
Methoxychlor 72-43-5
Total dust - 15 -
2-Methoxyethanol (Methyl cellosolve) 109-86-4 25 80 X
2-Methoxyethyl acetate (Methyl cellosolve acetate) 110-49-6 25 120 X
Methyl acetate 79-20-9 200 610 -
Methyl acetylene (Propyne) 74-99-7 1000 1650 -
Methyl acetylene-propadiene mixture (MAPP) 1000 1800 -
Methyl acrylate 96-33-3 10 35 X
Methylal (Dimethoxy-methane) 109-87-5 1000 3100 -
Methyl alcohol 67-56-1 200 260 -
Methylamine 74-89-5 10 12 -
Methyl amyl alcohol; see Methyl isobutyl carbinol
Methyl n-amyl ketone 110-43-0 100 465 -
Methyl bromide 74-83-9 (C)20 (C)80 X
Methyl butyl ketone; see 2-Hexanone
Methyl cellosolve; see 2-Methoxyethanol
Methyl cellosolve acetate; see 2-Methoxyethyl acetate
Methylene chloride; see §1910.1052
Methyl chloroform (1,1,1-Trichloroethane) 71-55-6 350 1900 -
Methylcyclohexane 108-87-2 500 2000 -
Methylcyclohexanol 25639-42-3 100 470 -
o-Methylcyclohexanone 583-60-8 100 460 X
Methylene chloride 75-09-2 500 1740 -
Methylenedianiline (MDA) 101-77-9
Methyl ethyl ketone (MEK); see 2-Butanone
Methyl formate 107-31-3 100 250 -
Methyl hydrazine (Monomethyl hydrazine) 60-34-4 (C)0.2 (C)0.35 X
Methyl iodide 74-88-4 5 28 X
Methyl isoamyl ketone 110-12-3 100 475 -
Methyl isobutyl carbinol 108-11-2 25 100 X
Methyl isobutyl ketone; see Hexone
Methyl isocyanate 624-83-9 0.02 0.05 X
Methyl mercaptan 74-93-1 0.5 1 -
Methyl methacrylate 80-62-6 100 410 -
Methyl propyl ketone; see 2-Pentanone
Methyl silicate 681-84-5 (C)5 (C)30 -
alpha-Methyl styrene 98-83-9 (C)100 (C)480 -
Methylene bisphenyl isocyanate (MDI) 101-68-8 (C)0.02 (C)0.2 -
Mica; see Silicates
Molybdenum (as Mo) 7439-98-7
Soluble compounds - 5 -
Insoluble compounds
Total dust - 15 -
Monomethyl aniline 100-61-8 2 9 X
Monomethyl hydrazine; see Methyl hydrazine
Morpholine 110-91-8 20 70 X
Naphtha (Coal tar) 8030-30-6 100 400 -
Naphthalene 91-20-3 10 50 -
alpha-Naphthylamine; see §1926.1104 134-32-7
beta-Naphthylamine; see §1926.1109 91-59-8 -
Neon 7440-01-9 E
Nickel carbonyl (as Ni) 13463-39-3 0.001 0.007 -
Nickel, metal and insoluble compounds (as Ni) 7440-02-0 - 1 -
Nickel, soluble compounds (as Ni) 7440-02-0 - 1 -
Nicotine 54-11-5 - 0.5 X
Nitric acid 7697-37-2 2 5 -
Nitric oxide 10102-43-9 25 30 -
p-Nitroaniline 100-01-6 1 6 X
Nitrobenzene 98-95-3 1 5 X
p-Nitrochlorobenzene 100-00-5 - 1 X
4-Nitrodiphenyl; see §1926.1103 92-93-3
Nitroethane 79-24-3 100 310 -
Nitrogen 7727-37-9 E
Nitrogen dioxide 10102-44-0 (C)5 (C)9 -
Nitrogen trifluoride 7783-54-2 10 29 -
Nitroglycerin 55-63-0 (C)0.2 (C)2 X
Nitromethane 75-52-5 100 250 -
1-Nitropropane 108-03-2 25 90 -
2-Nitropropane 79-46-9 25 90 -
N-Nitrosodimethylamine; see §1926.1116 62-79-9 -
Nitrotoluene (all isomers) 5 30 X
o-isomer 88-72-2;
m-isomer 99-08-1;
p-isomer 99-99-0
Nitrotrichloromethane; see Chloropicrin
Nitrous oxide 10024-97-2 E
Octachloronaphthalene 2234-13-1 - 0.1 X
Octane 111-65-9 400 1900 -
Oil mist, mineral 8012-95-1 - 5 -
Osmium tetroxide (as Os) 20816-12-0 - 0.002 -
Oxalic acid 144-62-7 - 1 -
Oxygen difluoride 7783-41-7 0.05 0.1 -
Ozone 10028-15-6 0.1 0.2 -
Paraquat, respirable dust 4685-14-7; - 0.5 X
Parathion 56-38-2 - 0.1 X
Particulates not otherwise regulated
Total dust organic and inorganic - 15 -
PCB; see Chlorodiphenyl (42% and 54% chlorine)
Pentaborane 19624-22-7 0.005 0.01 -
Pentachloronaphthalene 1321-64-8 - 0.5 X
Pentachlorophenol 87-86-5 - 0.5 X
Pentaerythritol 115-77-5
Total dust - -
Respirable fraction - -
Pentane 109-66-0 500 1500 -
2-Pentanone (Methyl propyl ketone) 107-87-9 200 700 -
Perchloroethylene (Tetrachloroethylene) 127-18-4 100 670 -
Perchloromethyl mercaptan 594-42-3 0.1 0.8 -
Perchloryl fluoride 7616-94-6 3 13.5 -
Petroleum distillates (Naphtha)(Rubber Solvent) A3 -
Phenol 108-95-2 5 19 X
p-Phenylene diamine 106-50-3 - 0.1 X
Phenyl ether, vapor 101-84-8 1 7 -
Phenyl ether-biphenyl mixture, vapor 1 7 -
Phenylethylene; see Styrene
Phenyl glycidyl ether (PGE) 122-60-1 10 60 -
Phenylhydrazine 100-63-0 5 22 X
Phosdrin (Mevinphos) 7786-34-7 - 0.1 X
Phosgene (Carbonyl chloride) 75-44-5 0.1 0.4 -
Phosphine 7803-51-2 0.3 0.4 -
Phosphoric acid 7664-38-2 - 1 -
Phosphorus (yellow) 7723-14-0 - 0.1 -
Phosphorus pentachloride 10026-13-8 - 1 -
Phosphorus pentasulfide 1314-80-3 - 1 -
Phosphorus trichloride 7719-12-2 0.5 3 -
Phthalic anhydride 85-44-9 2 12 -
Picric acid 88-89-1 - 0.1 X
Pindone (2-Pivalyl-1,3-indandione) 83-26-1 - 0.1 -
Plaster of Paris 26499-65-0
Total dust - -
Respirable fraction - -
Platinum (as Pt) 7440-06-4
Metal - - -
Soluble salts - 0.002 -
Polytetrafluoroethylene decomposition products A2
Portland cement 65997-15-1
Total dust - 15 -
Respirable fraction 5 -
Propane 74-98-6 E
Propargyl alcohol 107-19-7 1 - X
beta-Propriolactone; see §1926.1113 57-57-8
n-Propyl acetate 109-60-4 200 840 -
n-Propyl alcohol 71-23-8 200 500 -
n-Propyl nitrate 627-13-4 25 110 -
Propylene dichloride 78-87-5 75 350 -
Propylene imine 75-55-8 2 5 X
Propylene oxide 75-56-9 100 240 -
Propyne; see Methyl acetylene
Pyrethrum 8003-34-7 - 5 -
Pyridine 110-86-1 5 15 -
Quinone 106-51-4 0.1 0.4 -
RDX; see Cyclonite
Rhodium (as Rh), metal fume and insoluble compounds 7440-16-6 - 0.1 -
Rhodium (as Rh), soluble compounds 7440-16-6 - 0.001 -
Ronnel 299-84-3 - 10 -
Rotenone 83-79-4 - 5 -
Total dust - -
Respirable fraction - -
Selenium compounds (as Se) 7782-49-2 - 0.2 -
Selenium hexafluoride (as Se) 7783-79-1 0.05 0.4 -
Silica, amorphous, precipitated and gel 112926-00-8 (2) (2) (2)
Silica, amorphous, diatomaceous earth, containing less than 1% crystalline silica 61790-53-2 (2) (2) (2)
Silica, crystalline, respirable dust
Cristobalite; see 1926.1153 14464-46-1
Quartz; see 1926.11535 14808-60-7
Tripoli (as quartz); see 1926.11535 1317-95-9
Tridymite; see 1926.1153 15468-32-3
Silica, fused, respirable dust 60676-86-0 (2) (2) (2)
Silicates (less than 1% crystalline silica)
Mica (respirable dust) 12001-26-2 (2) (2) (2)
Soapstone, total dust (2) (2) (2)
Soapstone, respirable dust (2) (2) (2)
Talc (containing asbestos); use asbestos limit; see 1926.58
Talc (containing no asbestos), respirable dust 14807-96-6 (2) (2) (2)
Tremolite, asbestiform; see 1926.58
Silicon carbide 409-21-2
Total dust - -
Respirable fraction - -
Silver, metal and soluble compounds (as Ag) 7440-22-4 - 0.01 -
Soapstone; see Silicates
Sodium fluoroacetate 62-74-8 - 0.05 X
Sodium hydroxide 1310-73-2 - 2 -
Starch 9005-25-8
Total dust - -
Respirable fraction - -
Stibine 7803-52-3 0.1 0.5 -
Stoddard solvent 8052-41-3 200 1150 -
Strychnine 57-24-9 - 0.15 -
Styrene 100-42-5 (C)100 (C)420 -
Sucrose 57-50-1
Total dust - -
Respirable fraction - -
Sulfur dioxide 7446-09-5 5 13 -
Sulfur hexafluoride 2551-62-4 1000 6000 -
Sulfuric acid 7664-93-9 - 1 -
Sulfur monochloride 10025-67-9 1 6 -
Sulfur pentafluoride 5714-22-7 0.025 0.25 -
Sulfuryl fluoride 2699-79-8 5 20 -
Systox, see Demeton
2,4,5-T (2,4,5-trichlorophenoxyacetic acid) 93-76-5 - 10 -
Talc; see Silicates-
Tantalum, metal and oxide dust 7440-25-7 - 5 -
TEDP (Sulfotep) 3689-24-5 - 0.2 X
Teflon decomposition products A2
Tellurium and compounds (as Te) 13494-80-9 - 0.1 -
Tellurium hexafluoride (as Te) 7783-80-4 0.02 0.2 -
Temephos 3383-96-8
Total dust - -
Respirable fraction - -
TEPP (Tetraethyl pyrophosphate) 107-49-3 - 0.05 X
Terphenyls 26140-60-3 (C)1 (C)9 -
1,1,1,2-Tetrachloro-2,2-difluoroethane 76-11-9 500 4170 -
1,1,2,2-Tetrachloro-1,2-difluoroethane 76-12-0 500 4170 -
1,1,2,2-Tetrachloroethane 79-34-5 5 35 X
Tetrachloroethylene; see Perchloroethylene
Tetrachloromethane; see Carbon tetrachloride
Tetrachloronaphthalene 1335-88-2 - 2 X
Tetraethyl lead (as Pb) 78-00-2 - 0.1 X
Tetrahydrofuran 109-99-9 200 590 -
Tetramethyl lead, (as Pb) 75-74-1 - 0.15 X
Tetramethyl succinonitrile 3333-52-6 0.5 3 X
Tetranitromethane 509-14-8 1 8 -
Tetryl (2,4,6-Trinitrophenylmethylnitramine) 479-45-8 - 1.5 X
Thallium, soluble compounds (as Tl) 7440-28-0 - 0.1 X
Thiram 137-26-8 - 5 -
Tin, inorganic compounds (except oxides) (as Sn) 7440-31-5 - 2 -
Tin, organic compounds (as Sn) 7440-31-5 - 0.1 -
Tin oxide (as Sn) 21651-19-4 - - -
Total dust - -
Respirable fraction - -
Titanium dioxide 13463-67-7
Total dust - -
Toluene 108-88-3 200 750 -
Toluene-2,4-diisocyanate (TDI) 584-84-9 (C)0.02 (C)0.14 -
o-Toluidine 95-53-4 5 22 X
Toxaphene; see Chlorinated camphene
Tremolite; see Silicates
Tributyl phosphate 126-73-8 - 5 -
1,1,1-Trichloroethane; see Methyl chloroform
1,1,2-Trichloroethane 79-00-5 10 45 X
Trichloroethylene 79-01-6 100 535 -
Trichloromethane; see Chloroform
Trichloronaphthalene 1321-65-9 - 5 X
1,2,3-Trichloropropane 96-18-4 50 300 -
1,1,2-Trichloro-1,2,2-trifluoroethane 76-13-1 1000 7600 -
Triethylamine 121-44-8 25 100 -
Trifluorobromomethane 75-63-8 1000 6100 -
Trimethyl benzene 25551-13-7 25 120 -
2,4,6-Trinitrophenol; see Picric acid
2,4,6-Trinitrophenylmethylnitramine; see Tetryl
2,4,6-Trinitrotoluene (TNT) 118-96-7 - 1.5 X
Triorthocresyl phosphate 78-30-8 - 0.1 -
Triphenyl phosphate 115-86-6 - 3 -
Tungsten (as W) 7440-33-7
Insoluble compounds - 5 -
Soluble compounds - 1 -
Turpentine 8006-64-2 100 560 -
Uranium (as U) 7440-61-1
Soluble compounds - 0.2 -
Insoluble compounds - 0.2 -
Vanadium 1314-62-1
Respirable dust (as V2O5) - (C)0.5 -
Fume (as V2O5) - (C)0.1 -
Vegetable oil mist
Total dust - -
Respirable fraction - -
Vinyl benzene; see Styrene
Vinyl chloride; see §1926.1117 75-01-4
Vinyl cyanide; see Acrylonitrile
Vinyl toluene 25013-15-4 100 480 -
Warfarin 81-81-2 - 0.1 -
Xylenes (o-, m-, p-isomers) 1330-20-7 100 435 -
Xylidine 1300-73-8 5 25 X
Yttrium 7440-65-5 - 1 -
Zinc chloride fume 7646-85-7 - 1 -
Zinc oxide fume 1314-13-2 - 5 -
Zinc oxide 1314-13-2
Total dust - 15 -
Respirable fraction - 5 -
Zirconium compounds (as Zr) 7440-67-7 - 5

Mineral Dusts
Substance mppcf(j)
CrystallineQuartz. Threshold Limit calculated from the formula (p) 250(k)
%SiO2 + 5
Amorphous, including natural diatomaceous earth 20
SILICATES (less than 1% crystalline silica)
Mica 20
Portland cement 50
Soapstone 20
Talc (non-asbestiform) 20
Talc (fibrous), use asbestos limit --
Graphite (natural) 15
Inert or Nuisance Particulates:(m) 50 (or 15 mg/m3 whichever is the smaller) of total dust <1% SiO2
[Inert or Nuisance Dusts includes all mineral, inorganic, and organic dusts as indicated by examples in TLV's appendix D]
Conversion factors
mppcf × 35.3 = million particles per cubic meter = particles per c.c.


1 [Reserved]

2 See Mineral Dusts Table.

3 Use Asbestos Limit §1926.58.

4 See 1926.58.

5 See Mineral Dusts table for the exposure limit for any operations or sectors where the exposure limit in § 1926.1153 is stayed or is otherwise not in effect

* The PELs are 8-hour TWAs unless otherwise noted; a (C) designation denotes a ceiling limit.

** As determined from breathing-zone air samples.

a Parts of vapor or gas per million parts of contaminated air by volume at 25 °C and 760 torr.

b Milligrams of substance per cubic meter of air. When entry is in this column only, the value is exact; when listed with a ppm entry, it is approximate.

c [Reserved]

d The CAS number is for information only. Enforcement is based on the substance name. For an entry covering more than one metal compound, measured as the metal, the CAS number for the metal is given—not CAS numbers for the individual compounds.

e-f [Reserved]

g For sectors excluded from §1926.1128 the limit is 10 ppm TWA.

h-i [Reserved]

j Millions of particles per cubic foot of air, based on impinger samples counted by light-field techniques.

k The percentage of crystalline silica in the formula is the amount determined from airborne samples, except in those instances in which other methods have been shown to be applicable.

l [Reserved]

m Covers all organic and inorganic particulates not otherwise regulated. Same as Particulates Not Otherwise Regulated.

n If the exposure limit in §1926.1126 is stayed or is otherwise not in effect, the exposure limit is a ceiling of 0.1 mg/m3.

o If the exposure limit in §1926.1126 is stayed or is otherwise not in effect, the exposure limit is 0.1 mg/m3 (as CrO3) as an 8-hour TWA.

p This standard applies to any operations or sectors for which the respirable crystalline silica standard, 1926.1153, is stayed or otherwise is not in effect.

q This standard applies to any operations or sectors for which the beryllium standard, 1926.1124, is stayed or otherwise is not in effect.

The 1970 TLV uses letter designations instead of a numerical value as follows:

A1 [Reserved]

A2 Polytetrafluoroethylene decomposition products. Because these products decompose in part by hydrolysis in alkaline solution, they can be quantitatively determined in air as fluoride to provide an index of exposure. No TLV is recommended pending determination of the toxicity of the products, but air concentrations should be minimal.

A3 Gasoline and/or Petroleum Distillates. The composition of these materials varies greatly and thus a single TLV for all types of these materials is no longer applicable. The content of benzene, other aromatics and additives should be determined to arrive at the appropriate TLV.

E Simple asphyxiants. The limiting factor is the available oxygen which shall be at least 19.5% and be within the requirements addressing explosion in part 1926.

[39 FR 22801, June 24, 1974, as amended at 51 FR 37007, Oct. 17, 1986; 52 FR 46312, Dec 4, 1987; 58 FR 35089, June 30, 1993; 61 FR 9227, March 7, 1996; 61 FR 56746, Nov. 4, 1996; 62 FR 1493, Jan. 10, 1997; 71 FR 10381, Feb. 28, 2006; 81 FR 16875, March 25, 2016; 81 FR 60273-60274, September 1, 2016; 82 FR 2750-2751, Jan. 9, 2017]
Construction areas, ramps, runways, corridors, offices, shops, and storage areas shall be lighted to not less than the minimum illumination intensities listed in Table D-3 while any work is in progress:


Foot-Candles Area of Operation
5 General construction area lighting.
3 General construction areas, concrete placement
excavation and waste areas, access ways, active
storage areas, loading platforms, refueling, and
field maintenance areas.
5 Indoors: warehouses, corridors, hallways, and
5 Tunnels, shafts, and general underground work areas:
(Exception: minimum of 10 foot-candles is required
at tunnel and shaft heading during drilling,
mucking, and scaling. Bureau of Mines approved cap
lights shall be acceptable for use in the tunnel
10 General construction plant and shops (e.g., batch
plants, screening plants, mechanical and
electrical equipment rooms, carpenter shops,
rigging lofts and active store rooms, mess halls,
and indoor toilets and workrooms.)
30 First aid stations, infirmaries, and offices.
For areas or operations not covered above, refer to the American National Standard A11.1-1965, R1970, Practice for Industrial Lighting, for recommended values of illumination.
Whenever hazardous substances such as dusts, fumes, mists, vapors, or gases exist or are produced in the course of construction work, their concentrations shall not exceed the limits specified in 1926.55(a). When ventilation is used as an engineering control method, the system shall be installed and operated according to the requirements of this section.
Local exhaust ventilation when used as described in (a) shall be designed to prevent dispersion into the air of dusts, fumes, mists, vapors, and gases in concentrations causing harmful exposure. Such exhaust systems shall be so designed that dusts, fumes, mists, vapors, or gases are not drawn through the work area of employees.
Exhaust fans, jets, ducts, hoods, separators, and all necessary appurtenances, including refuse receptacles, shall be so designed, constructed, maintained and operated as to ensure the required protection by maintaining a volume and velocity of exhaust air sufficient to gather dusts, fumes, vapors, or gases from said equipment or process, and to convey them to suitable points of safe disposal, thereby preventing their dispersion in harmful quantities into the atmosphere where employees work.
The exhaust system shall be in operation continually during all operations which it is designed to serve. If the employee remains in the contaminated zone, the system shall continue to operate after the cessation of said operations, the length of time to depend upon the individual circumstances and effectiveness of the general ventilation system.
Since dust capable of causing disability is, according to the best medical opinion, of microscopic size, tending to remain for hours in suspension in still air, it is essential that the exhaust system be continued in operation for a time after the work process or equipment served by the same shall have ceased, in order to ensure the removal of the harmful elements to the required extent. For the same reason, employees wearing respiratory equipment should not remove same immediately until the atmosphere seems clear.
The air outlet from every dust separator, and the dusts, fumes, mists, vapors, or gases collected by an exhaust or ventilating system shall discharge to the outside atmosphere. Collecting systems which return air to work area may be used if concentrations which accumulate in the work area air do not result in harmful exposure to employees. Dust and refuse discharged from an exhaust system shall be disposed of in such a manner that it will not result in harmful exposure to employees.
A solid substance used in an abrasive blasting operation.
A complete enclosure which rotates on an axis, or which has an internal moving tread to tumble the parts, in order to expose various surfaces of the parts to the action of an automatic blast spray.
A complete enclosure in which blasting operations are performed and where the operator works inside of the room to operate the blasting nozzle and direct the flow of the abrasive material.
An air purifying respirator, commonly referred to as a dust or a fume respirator, which removes most of the dust or fume from the air passing through the device.
An enclosure where the operator stands outside and operates the blasting nozzle through an opening or openings in the enclosure.
Air of such purity that it will not cause harm or discomfort to an individual if it is inhaled for extended periods of time.
A device or combination of devices for separating dust from the air handled by an exhaust ventilation system.
A system for removing contaminated air from a space, comprising two or more of the following elements (A) enclosure or hood, (B) duct work, (C) dust collecting equipment, (D) exhauster, and (E) discharge stack.
Airborne dust in sizes capable of passing through the upper respiratory system to reach the lower lung passages.
An enclosure where the pieces to be cleaned are positioned on a rotating table and are passed automatically through a series of blast sprays.
The forcible application of an abrasive to a surface by pneumatic pressure, hydraulic pressure, or centrifugal force.
A respirator constructed so that it covers the wearer's head, neck, and shoulders to protect the wearer from rebounding abrasive.
Abrasives and the surface coatings on the materials blasted are shattered and pulverized during blasting operations and the dust formed will contain particles of respirable size. The composition and toxicity of the dust from these sources shall be considered in making an evaluation of the potential health hazards.
Organic abrasives which are combustible shall be used only in automatic systems. Where flammable or explosive dust mixtures may be present, the construction of the equipment, including the exhaust system and all electric wiring, shall conform to the requirements of American National Standard Installation of Blower and Exhaust Systems for Dust, Stock, and Vapor Removal or Conveying, Z33.1-1961 (NFPA 91-1961), and Subpart S of this part. The blast nozzle shall be bonded and grounded to prevent the build up of static charges. Where flammable or explosive dust mixtures may be present, the abrasive blasting enclosure, the ducts, and the dust collector shall be constructed with loose panels or explosion venting areas, located on sides away from any occupied area, to provide for pressure relief in case of explosion, following the principles set forth in the National Fire Protection Association Explosion venting Guide. NFPA 68-1954.
The concentration of respirable dust or fume in the breathing zone of the abrasive-blasting operator or any other worker shall be kept below the levels specified in 1926.55 or other pertinent sections of this part.
Blast-cleaning enclosures shall be exhaust ventilated in such a way that a continuous inward flow of air will be maintained at all openings in the enclosure during the blasting operation.
All air inlets and access openings shall be baffled or so arranged that by the combination of inward air flow and baffling the escape of abrasive or dust particles into an adjacent work area will be minimized and visible spurts of dust will not be observed.
The rate of exhaust shall be sufficient to provide prompt clearance of the dust-laden air within the enclosure after the cessation of blasting.
Before the enclosure is opened, the blast shall be turned off and the exhaust system shall be run for a sufficient period of time to remove the dusty air within the enclosure.
Safety glass protected by screening shall be used in observation windows, where hard deep-cutting abrasives are used.
Slit abrasive-resistant baffles shall be installed in multiple sets at all small access openings where dust might escape, and shall be inspected regularly and replaced when needed.
Doors shall be flanged and tight when closed.
Door on blast-cleaning rooms shall be operable from both inside and outside, except that where there is a small operator access door, the large work access door may be closed or opened from the outside only.
The construction, installation, inspection, and maintenance of exhaust systems shall conform to the principles and requirements set forth in American National Standard Fundamentals Governing the Design and Operation of Local Exhaust Systems, Z9.2-1960, and ANSI Z33.1-1961.
When dust leaks are noted, repairs shall be made as soon as possible.
The static pressure drop at the exhaust ducts leading from the equipment shall be checked when the installation is completed and periodically thereafter to assure continued satisfactory operation. Whenever an appreciable change in the pressure drop indicates a partial blockage, the system shall be cleaned and returned to normal operating condition.
The air exhausted from blast-cleaning equipment shall be discharged through dust collecting equipment. Dust collectors shall be set up so that the accumulated dust can be emptied and removed without contaminating other working areas.
In installation where the abrasive is recirculated, the exhaust ventilation system for the blasting enclosure shall not be relied upon for the removal of fines from the spent abrasive instead of an abrasive separator. An abrasive separator shall be provided for the purpose.
Employers must use only respirators approved by NIOSH under 42 CFR part 84 for protecting employees from dusts produced during abrasive-blasting operations.
Properly fitted particulate-filter respirators, commonly referred to as dust-filter respirators, may be used for short, intermittent, or occasional dust exposures such as cleanup, dumping of dust collectors, or unloading shipments of sand at a receiving point when it is not feasible to control the dust by enclosure, exhaust ventilation, or other means. The respirators used must be approved by NIOSH under 42 CFR part 84 for protection against the specific type of dust encountered.
A respiratory protection program as defined and described in 1926.103, shall be established wherever it is necessary to use respiratory protective equipment.
Operators shall be equipped with heavy canvas or leather gloves and aprons or equivalent protection to protect them from the impact of abrasives. Safety shoes shall be worn to protect against foot injury where heavy pieces of work are handled.
Safety shoes shall conform to the requirements of American National Standard for Men's Safety-Toe Footwear, Z41.1-1967.
Equipment for protection of the eyes and face shall be supplied to the operator when the respirator design does not provide such protection and to any other personnel working in the vicinity of abrasive blasting operations. This equipment shall conform to the requirements of 1926.102.
Abrasive-blasting respirators shall be worn by all abrasive-blasting operators:
When working inside of blast-cleaning rooms, or
When using silica sand in manual blasting operations where the nozzle and blast are not physically separated from the operator in an exhaust ventilated enclosure, or
Where concentrations of toxic dust dispersed by the abrasive blasting may exceed the limits set in 1926.55 or other pertinent sections of this part and the nozzle and blast are not physically separated from the operator in an exhaust-ventilated enclosure.
Air for abrasive-blasting respirators must be free of harmful quantities of dusts, mists, or noxious gases, and must meet the requirements for supplied-air quality and use specified in 29 CFR 1910.134(i).
Dust shall not be permitted to accumulate on the floor or on ledges outside of an abrasive-blasting enclosure, and dust spills shall be cleaned up promptly. Aisles and walkways shall be kept clear of steel shot or similar abrasive which may create a slipping hazard.
This paragraph applies to all operations where an abrasive is forcibly applied to a surface by pneumatic or hydraulic pressure, or by centrifugal force. It does not apply to steam blasting, or steam cleaning, or hydraulic cleaning methods where work is done without the aid of abrasives.
Organic-bonded wheels, the thickness of which is not more than one forty-eighth of their diameter for those up to, and including, 20 inches (50.8 cm) in diameter, and not more than one-sixtieth of their diameter for those larger than 20 inches (50.8 cm) in diameter, used for a multitude of operations variously known as cutting, cutting off, grooving, slotting, coping, and jointing, and the like. The wheels may be "solid" consisting of organic-bonded abrasive material throughout, "steel centered" consisting of a steel disc with a rim of organic-bonded material molded around the periphery, or of the "inserted tooth" type consisting of a steel disc with organic-bonded abrasive teeth or inserts mechanically secured around the periphery.
The part of an exhaust system piping that is connected directly to the hood or enclosure.
A movable fixture, upon which the part to be ground or polished is placed.
A pipe into which one or more branch pipes enter and which connects such branch pipes to the remainder of the exhaust system.
All power-driven rotatable discs faced with abrasive materials, artificial or natural, and used for grinding or polishing on the side of the assembled disc.
The loss in static pressure caused by air flowing into a duct or hood. It is usually expressed in inches of water gauge.
A system consisting of branch pipes connected to hoods or enclosures, one or more header pipes, an exhaust fan, means for separating solid contaminants from the air flowing in the system, and a discharge stack to outside.
All power-driven rotatable grinding or abrasive wheels, except disc wheels as defined in this standard, consisting of abrasive particles held together by artificial or natural bonds and used for peripheral grinding.
The partial or complete enclosure around the wheel or disc through which air enters an exhaust system during operation.
A grinding machine carrying two power-driven, rotatable, coaxial, horizontal spindles upon the inside ends of which are mounted abrasive disc wheels used for grinding two surfaces simultaneously.
A grinding machine carrying an abrasive disc wheel upon one or both ends of a power-driven, rotatable single horizontal spindle.
All power-driven rotatable wheels composed all or in part of textile fabrics, wood, felt, leather, paper, and may be coated with abrasives on the periphery of the wheel for purposes of polishing, buffing, and light grinding.
Any power-driven rotatable grinding, polishing, or buffing wheel mounted in such manner that it may be manually manipulated.
All power-driven rotatable wheels made from wire or bristles, and used for scratch cleaning and brushing purposes.
Any power-driven rotatable grinding, polishing, or buffing wheel mounted in such a manner that the wheel with its supporting framework can be manipulated over stationary objects.
The kinetic pressure in the direction of flow necessary to cause a fluid at rest to flow at a given velocity. It is usually expressed in inches of water gauge.
A grinding machine having a vertical, rotatable power-driven spindle carrying a horizontal abrasive disc wheel.
All power-driven, flexible, coated bands used for grinding, polishing, or buffing purposes.
Wherever dry grinding, dry polishing or buffing is performed, and employee exposure, without regard to the use of respirators, exceeds the permissible exposure limits prescribed in 1926.55 or other pertinent sections of this part, a local exhaust ventilation system shall be provided and used to maintain employee exposures within the prescribed limits.
Hoods connected to exhaust systems shall be used, and such hoods shall be designed, located, and placed so that the dust or dirt particles shall fall or be projected into the hoods in the direction of the air flow. No wheels, discs, straps, or belts shall be operated in such manner and in such direction as to cause the dust and dirt particles to be thrown into the operator's breathing zone.
Scratch-brush wheels and all buffing and polishing wheels mounted on floor stands, pedestals, benches, or special-purpose machines shall have not less than the minimum exhaust volume shown in Table D-57.2.

Wheel diameter, inches (cm) Wheel width,
inches (cm)
Minimum exhaust
To 9 (22.86) 2 (5.08) 300
Over 9 to 16 (22.86 to 40.64) 3 (7.62) 500
Over 16 to 19
(40.64 to 48.26)
4 (10.16) 610
Over 19 to 24
(48.26 to 60.96)
5 (12.7) 740
Over 24 to 30
(60.96 to 76.2)
6 (15.24) 1,040
Over 30 to 36
(76.2 to 91.44)
6 (15.24) 1,200

Grinding wheels or discs for horizontal single-spindle disc grinders shall be hooded to collect the dust or dirt generated by the grinding operation and the hoods shall be connected to branch pipes having exhaust volumes as shown in Table D-57.3.

Disc diameter, inches (cm) Exhaust volume (feet3/min.)
Upto 12 (30.48) 220
Over 12 to 19 (30.48 to 48.26) 390
Over 19 to 30 (48.26 to 76.2) 610
Over 30 to 36 (76.2 to 91.44) 880
Where the work is outside the hood, air volumes must be increased as shown in American Standard Fundamentals Governing the Design and Operation of Local Exhaust Systems, Z9.2-1960 (section 4, exhaust hoods).
Grinding wheels or discs for horizontal double-spindle disc grinders shall have a hood enclosing the grinding chamber and the hood shall be connected to one or more branch pipes having exhaust volumes as shown in Table D-57.4.

Disc diameter, inches (cm) Exhaust volume (feet3/min.)
Up to 19 (48.26) 610
Over 19 to 25 (48.26 to 63.5) 880
Over 25 to 30 (63.5 to 76.2) 1,200
Over 30 to 53 (76.2 to 134.62) 1,770
Over 53 to 72 (134.62 to 182.88) 6,280
Grinding wheels or discs for vertical single-spindle disc grinders shall be encircled with hoods to remove the dust generated in the operation. The hoods shall be connected to one or more branch pipes having exhaust volumes as shown in Table D-57.5.

Disc diameter, inches (cm) One-half or more of disc covered Disc not covered
Number1 Exhaust foot3/min. Number1 Exhaust foot3/min.
Up to 20 (50.8) 1 500 2 780
Over 20 to 30 (50.8 to 76.2) 2 780 2 1,480
Over 30 to 53 (76.2 to 134.62) 2 1,770 4 3,530
Over 53 to 72 (134.62 to 182.88) 2 3,140 5 6,010

   Footnote(1) Number of exhaust outlets around periphery of hood, or equal distribution provided by other means.
Grinding and polishing belts shall be provided with hoods to remove dust and dirt generated in the operations and the hoods shall be connected to branch pipes having exhaust volumes as shown in Table D-57.6.

Belts width, inches (cm) Exhaust volume (feet3/min.)
Up to 3 (7.62) 220
Over 3 to 5 (7.62 to 12.7) 300
Over 5 to 7 (12.7 to 17.78) 390
Over 7 to 9 (17.78 to 22.86) 500
Over 9 to 11 (22.86 to 27.94) 610
Over 11 to 13 (27.94 to 33.02) 740
Cradles and swing-frame grinders. Where cradles are used for handling the parts to be ground, polished, or buffed, requiring large partial enclosures to house the complete operation, a minimum average air velocity of 150 feet per minute shall be maintained over the entire opening of the enclosure. Swing-frame grinders shall also be exhausted in the same manner as provided for cradles. (See fig. D-57.3)
Grinding wheels on floor stands, pedestals, benches, and special-purpose grinding machines and abrasive cutting-off wheels shall have not less than the minimum exhaust volumes shown in Table D-57.1 with a recommended minimum duct velocity of 4,500 feet per minute in the branch and 3,500 feet per minute in the main. The entry losses from all hoods except the vertical-spindle disc grinder hood, shall equal 0.65 velocity pressure for a straight takeoff and 0.45 velocity pressure for a tapered takeoff. The entry loss for the vertical-spindle disc grinder hood is shown in figure D-57.1 (following paragraph (g) of this section).

Wheel diameter, inches (cm) Wheel width,
inches (cm)
Minimum exhaust
To 9 (22.86) 11/2 (3.81) 220
Over 9 to 16 (22.86 to 40.64) 2 (5.08) 390
Over 16 to 19
(40.64 to 48.26)
3 (7.62) 500
Over 19 to 24
(48.26 to 60.96)
4 (10.16) 610
Over 24 to 30
(60.96 to 76.2)
5 (12.7) 880
Over 30 to 36
(76.2 to 91.44)
6 (15.24) 1,200

For any wheel wider than wheel diameters shown in Table D-57.1, increase the exhaust volume by the ratio of the new width to the width shown.


If wheel width = 41/2 inches (11.43 cm), then (4.5/4) x 610 = 686 (rounded to 690).

Exhaust systems for grinding, polishing, and buffing operations should be designed in accordance with American Standard Fundamentals Governing the Design and Operation of Local Exhaust Systems, Z9.2-1960.
All exhaust systems shall be provided with suitable dust collectors.
Exhaust systems for grinding, polishing, and buffing operations shall be tested in the manner described in American Standard Fundamentals Governing the Design and Operation of Local Exhaust Systems, Z9.2-1960.
It is the dual function of grinding and abrasive cutting-off wheel hoods to protect the operator from the hazards of bursting wheels as well as to provide a means for the removal of dust and dirt generated. All hoods shall be not less in structural strength than specified in the American National Standard Safety Code for the Use, Care, and Protection of Abrasive Wheels, B7.1-1970.
Due to the variety of work and types of grinding machines employed, it is necessary to develop hoods adaptable to the particular machine in question, and such hoods shall be located as close as possible to the operation.
Swing-frame grinders shall be provided with exhaust booths as indicated in figure D-57.3.
Figure D-57.3 -- A Method of Applying an Exhaust Enclosure to Swing-Frame Grinders
Portable grinding operations, whenever the nature of the work permits, shall be conducted within a partial enclosure. The opening in the enclosure shall be no larger than is actually required in the operation and an average face air velocity of not less than 200 feet per minute shall be maintained.
Vertical-spindle disc grinders shall be encircled with a hood so constructed that the heavy dust is drawn off a surface of the disc and the lighter dust exhausted through a continuous slot at the top of the hood as shown in figure D-57.1.
Figure D-57.1 -- Vertical Spindle Disc Grinder Exhaust Hood and Branch Pipe Connections

Dia. D inches (cm) Exhaust E Volume
at 4,500
Min. Max. No Pipes Dia.
1 4 1/4
500 When
or more
of the
disc can
be hooded,
ducts as
shown at
the left.
Over 20 (50.8) 30
2 4
Over 30 (76.2) 72
2 6
Over 53 (134.62) 72
2 8
2 4
780 When no
hood can
be used
at left.
Over 20 (50.8) 20
2 4
Over 30 (76.2) 30
2 5 1/2
Over 53 (134.62) 53
4 6

Entry loss=1.0 slot velocity pressure + 0.5 branch velocity pressure. Minimum slot velocity=2,000 ft/min -- 1/2-inch (1.27 cm) slot width.
Hoods for polishing and buffing, and scratch-brush wheels shall be constructed to conform as closely to figure D-57.4 as the nature of the work will permit.
Figure D-57.4

Standard Buffing and Polishing Hood
Wheel dimension, inches (centimeters Exhaust
of air
Diameter Width, Max
Min= d Max= D
9 (22.86) 2 (5.08) 31/2 (3.81) 300
Over 9 (22.86) 16 (40.64) 3 (5.08) 4 500
Over 16 (40.64) 19 (48.26) 4 (11.43) 5 610
Over 19 (48.26) 24 (60.96) 5 (12.7) 51/2 740
Over 24 (60.96) 30 (76.2) 6 (15.24) 61/2 1,040
Over 30 (76.2) 36 (91.44) 6 (15.24) 7 1,200
Entry loss = 0.15 velocity pressure for tapered takeoff; 0.65 velocity pressure for straight takeoff.
Cradle grinding and polishing operations shall be performed within a partial enclosure similar to figure D-57.5. The operator shall be positioned outside the working face of the opening of the enclosure. The face opening of the enclosure should not be any greater in area than that actually required for the performance of the operation and the average air velocity into the working face of the enclosure shall not be less than 150 feet per minute.
Figure D-57.5 -- Cradle Polishing or Grinding Enclosure
Entry loss = 0.45 velocity pressure for tapered takeoff.
Hoods for horizontal single-spindle disc grinders shall be constructed to conform as closely as possible to the hood shown in figure D-57.6. It is essential that there be a space between the back of the wheel and the hood, and a space around the periphery of the wheel of at least 1 inch (2.54 cm) in order to permit the suction to act around the wheel periphery. The opening on the side of the disc shall be no larger than is required for the grinding operation, but must never be less than twice the area of the branch outlet.
Figure D-57.6 -- Horizontal Single-Spindle Disc Grinder Exhaust Hood and Branch Pipe Connections

Dia D inches (centimeters) Exhaust E
at 4,500
Min. Max.
12 (30.48) 3 (7.6) 220
Over 12 (30.48) 19 (48.26) 4 (10.16) 390
Over 19 (48.26) 30 (76.2) 5 (12.7) 610
Over 30 (76.2) 36 (91.44) 6 (15.24) 880

NOTE: If grinding wheels are used for disc grinding purposes, hoods must conform to structural strength and materials as described in 9.1.

Entry loss = 0.45 velocity pressure for tapered takeoff.
Horizontal double-spindle disc grinders shall have a hood encircling the wheels and grinding chamber similar to the illustrated in figure D-57.7. The openings for passing the work into the grinding chamber should be kept as small as possible, but must never be less than twice the area of the branch outlets.
Figure D-57.7 -- Horizontal Double-Spindle Disc Grinder Exhaust Hood and Branch Pipe Connections

Disc dia.inches
Exhaust E Volume
at 4,500
Min. Max. No
1 5 610
Over 19 (48.26) 25
1 6 880 When
width "W" permits, exhaust ducts
be as
near heaviest grinding
as possible.
Over 25 (63.5) 30
1 7 1,200
Over 30 (76.2 53 (134.62) 2 6 1,770
Over 53 (134.62) 72
4 8 6,280
Entry loss = 0.45 velocity pressure for tapered takeoff.
Grinding and polishing belt hoods shall be constructed as close to the operation as possible. The hood should extend almost to the belt, and 1-inch (2.54 cm) wide openings should be provided on either side.
Figure D-57.8 -- A Typical Hood for a Belt Operation

Entry loss = 0.45 velocity pressure for tapered takeoff.

Belt width W. inches (centimeters) Exhaust Volume
Up to 3 (7.62) 220
3 to 5 (7.62 to 12.7) 300
5 to 7 (12.7 to 17.78) 390
7 to 9 (17.78 to 22.86) 500
9 to 11 (22.86 to 27.94) 610
11 to 13 (27.94 to 33.02) 740
Minimum duct velocity = 4,500 ft/min branch, 3,500 ft/min main.
Entry loss = 0.45 velocity pressure for tapered takeoff; 0.65 velocity pressure for straight takeoff.
Exhaust hoods for floor stands, pedestals, and bench grinders shall be designed in accordance with figure D-57.2. The adjustable tongue shown in the figure shall be kept in working order and shall be adjusted within one-fourth inch (0.635 cm) of the wheel periphery at all times.
Figure D-57.2 -- Standard Grinder Hood

Wheel dimension, inches (centimeters Exhaust
of air
Diameter Width, Max
Min= d Max= D
9 (22.86) 1 1/2 (3.81) 3 220
Over 9 (22.86) 16 (40.64) 2 (5.08) 4 390
Over 16 (40.64) 19 (48.26) 3 (7.62) 4 1/2 500
Over 19 (48.26) 24 (60.96) 4 (10.16) 5 610
Over 24 (60.96) 30 (76.2) 5 (12.7) 6 880
Over 30 (76.2) 36 (91.44) 6 (15.24) 7 1,200
Entry loss = 0.45 velocity pressure for tapered takeoff 0.65 velocity pressure for straight takeoff.
This paragraph (g), prescribes the use of exhaust hood enclosures and systems in removing dust, dirt, fumes, and gases generated through the grinding, polishing, or buffing of ferrous and nonferrous metals.
Spray-finishing operations are employment of methods wherein organic or inorganic materials are utilized in dispersed form for deposit on surfaces to be coated, treated, or cleaned. Such methods of deposit may involve either automatic, manual, or electrostatic deposition but do not include metal spraying or metallizing, dipping, flow coating, roller coating, tumbling, centrifuging, or spray washing and degreasing as conducted in self-contained washing and degreasing machines or systems.
A spray room is a room in which spray-finishing operations not conducted in a spray booth are performed separately from other areas.
Minimum maintained velocity is the velocity of air movement which must be maintained in order to meet minimum specified requirements for health and safety.
Spray booths are defined and described in 1926.66(a). (See sections 103, 104, and 105 of the Standard for Spray Finishing Using Flammable and Combustible Materials, NFPA No. 33-1969).
Spray booths or spray rooms are to be used to enclose or confine all operations. Spray-finishing operations shall be located as provided in sections 201 through 206 of the Standard for Spray Finishing Using Flammable and Combustible Materials, NFPA No. 33-1969.
Spray booths shall be designed and constructed in accordance with 1926.66(b)(1) through (4) and (6) through (10)(see sections 301-304 and 306-310 of the Standard for Spray Finishing Using Flammable and Combustible Materials, NFPA No. 33-1969), for general construction specifications. For a more detailed discussion of fundamentals relating to this subject, see ANSI Z9.2-1960.
Lights, motors, electrical equipment, and other sources of ignition shall conform to the requirements of 1926.66(b)(10) and (c). (See section 310 and chapter 4 of the Standard for Spray Finishing Using Flammable and Combustible Materials NFPA No. 33-1969.)
In no case shall combustible material be used in the construction of a spray booth and supply or exhaust duct connected to it.
Baffles, distribution plates, and dry-type overspray collectors shall conform to the requirements of 1926.66(b)(4) and (5). (See sections 304 and 305 of the Standard for Spray Finishing Using Flammable and Combustible Materials, NFPA No. 33-1969.)
Overspray filters shall be installed and maintained in accordance with the requirements of 1926.66(b)(5), (see section 305 of the Standard for Spray Finishing Using Flammable and Combustible Materials, NFPA No. 33-1969), and shall only be in a location easily accessible for inspection, cleaning, or replacement.
Where effective means, independent of the overspray filters, are installed which will result in design air distribution across the booth cross section, it is permissible to operate the booth without the filters in place.
For wet or water-wash spray booths, the water-chamber enclosure, within which intimate contact of contaminated air and cleaning water or other cleaning medium is maintained, if made of steel, shall be 18 gage or heavier and adequately protected against corrosion.
Chambers may include scrubber spray nozzles, headers, troughs, or other devices. Chambers shall be provided with adequate means for creating and maintaining scrubbing action for removal of particulate matter from the exhaust air stream.
Collecting tanks shall be of welded steel construction or other suitable non-combustible material. If pits are used as collecting tanks, they shall be concrete, masonry, or other material having similar properties.
Tanks shall be provided with weirs, skimmer plates, or screens to prevent sludge and floating paint from entering the pump suction box. Means for automatically maintaining the proper water level shall also be provided. Fresh water inlets shall not be submerged. They shall terminate at least one pipe diameter above the safety overflow level of the tank.
Tanks shall be so constructed as to discourage accumulation of hazardous deposits.
Pump manifolds, raisers, and headers shall be adequately sized to insure sufficient water flow to provide efficient operation of the water chamber.
Unobstructed walkways shall not be less than 6 1/2 feet (1.976 m) high and shall be maintained clear of obstruction from any work location in the booth to a booth exit or open booth front. In booths where the open front is the only exit, such exits shall be not less than 3 feet (0.912 m) wide. In booths having multiple exits, such exits shall not be less than 2 feet (0.608 m) wide, provided that the maximum distance from the work location to the exit is 25 feet (7.6 m) or less. Where booth exits are provided with doors, such doors shall open outward from the booth.
Spray rooms, including floors, shall be constructed of masonry, concrete, or other noncombustible material.
Spray rooms shall be adequately ventilated so that the atmosphere in the breathing zone of the operator shall be maintained in accordance with the requirements of paragraph (h)(6)(ii) of this section.
Spray rooms used for production spray-finishing operations shall conform to the requirements for spray booths.
Spray rooms shall have noncombustible fire doors and shutters.
Ventilation shall be provided in accordance with provisions of 1926.66(d)(see chapter 5 of the Standard for Spray Finishing Using Flammable or Combustible Materials, NFPA No. 33-1969); and in accordance with the following:
Where a fan plenum is used to equalize or control the distribution of exhaust air movement through the booth, it shall be of sufficient strength or rigidity to withstand the differential air pressure or other superficially imposed loads for which the equipment is designed and also to facilitate cleaning. Construction specifications shall be at least equivalent to those of paragraph (h)(5)(iii) of this section.
Exhaust ductwork shall be adequately supported throughout its length to sustain its weight plus any normal accumulation in interior during normal operating conditions and any negative pressure exerted upon it.
Exhaust ductwork shall be sized in accordance with good design practice which shall include consideration of fan capacity, length of duct, number of turns and elbows, variation in size, volume, and character of materials being exhausted. See American National Standard Z9.2-1960 for further details and explanation concerning elements of design.
Longitudinal joints in sheet steel ductwork shall be either lock-seamed, riveted, or welded. For other than steel construction, equivalent securing of joints shall be provided.
Circumferential joints in ductwork shall be substantially fastened together and lapped in the direction of airflow. At least every fourth joint shall be provided with connecting flanges, bolted together, or of equivalent fastening security.
Inspection or clean-out doors shall be provided for every 9 to 12 feet (2.736 to 3.648 m) of running length for ducts up to 12 inches (0.304 m) in diameter, but the distance between clean-out doors may be greater for larger pipes. (See 8.3.21 of American National Standard Z9.1-1951.) A clean-out door or doors shall be provided for servicing the fan and where necessary, a drain shall be provided.
Where ductwork passes through a combustible roof or wall, the roof or wall shall be protected at the point of penetration by open space or fire-resistive material between the duct and the roof or wall. When ducts pass through firewalls, they shall be provided with automatic fire dampers on both sides of the wall, except that three-eighth-inch steel plates may be used in lieu of automatic fire dampers for ducts not exceeding 18 inches (45.72 cm) in diameter.
Ductwork used for ventilating any process covered in this standard shall not be connected to ducts ventilating any other process or any chimney or flue used for conveying any products of combustion.
Inlet or supply ductwork used to transport makeup air to spray booths or surrounding areas shall be constructed of noncombustible materials.
If negative pressure exists within inlet ductwork, all seams and joints shall be sealed if there is a possibility of infiltration of harmful quantities of noxious gases, fumes, or mists from areas through which ductwork passes.
Inlet ductwork shall be sized in accordance with volume flow requirements and provide design air requirements at the spray booth.
Inlet ductwork shall be adequately supported throughout its length to sustain at least its own weight plus any negative pressure which is exerted upon it under normal operating conditions.
Except where a spray booth has an adequate air replacement system, the velocity of air into all openings of a spray booth shall be not less than that specified in Table D-57.7 for the operating conditions specified. An adequate air replacement system is one which introduces replacement air upstream or above the object being sprayed and is so designed that the velocity of air in the booth cross section is not less than that specified in Table D-57.7 when measured upstream or above the object being sprayed.


Operating conditions
for objects
completely inside
Airflow velocities, f.p.m.
Design Range
Electrostatic and
automatic airless
operation contained
in booth without operator.
Negligible 50 large booth 50-75

100 small booth 75-125
Air-operated guns,manual or automatic Up to 50 100 large booth 75-125
150 large booth 125-175
Air-operated guns,
manual or automatic
Up to 100 150 large booth 125-175
100 large booth 150-250
   Footnote(1) Attention is invited to the fact that the effectiveness of the spray booth is dependent upon the relationship of the depth of the booth to its height and width. Footnote(2) Crossdrafts can be eliminated through proper design and such design should be sought. Crossdrafts in excess of 100fpm (feet per minute) should not be permitted. Footnote(3) Excessive air pressures result in loss of both efficiency and material waste in addition to creating a backlash that may carry overspray and fumes into adjacent work areas. Footnote(4) Booths should be designed with velocities shown in the column headed "Design." However, booths operating with velocities shown in the column headed "Range" are in compliance with this standard.
When an operator is in a booth downstream of the object being sprayed, an air-supplied respirator or other type of respirator approved by NIOSH under 42 CFR Part 84 for the material being sprayed should be used by the operator.
Where downdraft booths are provided with doors, such doors shall be closed when spray painting.
In addition to the requirements in paragraph (h)(6)(i) of this section the total air volume exhausted through a spray booth shall be such as to dilute solvent vapor to at least 25 percent of the lower explosive limit of the solvent being sprayed. An example of the method of calculating this volume is given below.

Example: To determine the lower explosive limits of the most common solvents used in spray finishing, see Table D-57.8. Column 1 gives the number of cubic feet of vapor per gallon of solvent and column 2 gives the lower explosive limit (LEL) in percentage by volume of air. Note that the quantity of solvent will be diminished by the quantity of solids and nonflammables contained in the finish.

To determine the volume of air in cubic feet necessary to dilute the vapor from 1 gallon of solvent to 25 percent of the lower explosive limit, apply the following formula:

Dilution volume required per gallon of solvent = 4 (100-LEL) (cubic
   feet of vapor per gallon) + LEL

Using toluene as the solvent.
  1. LEL of toluene from Table D-57.8, column 2, is 1.4 percent.
  2. Cubic feet of vapor per gallon from Table D-57.8, column 1, is 30.4 cubic feet per gallon.
  3. Dilution volume required = 4 (100-1.4) 30.4 ÷ 1.4 = 8,564 cubic feet.
  4. To convert to cubic feet per minute of required ventilation, multiply the dilution volume required per gallon of solvent by the number of gallons of solvent evaporated per minute.

Solvent Cubic feet per
gallon of vapor
of liquid
at 70 deg. F
(21.11 deg. C).
Lower explosive
limit in percent
by volume of
air at 70 deg. F
(21.11 deg. C)
Column 1 Column 2
Acetone 44.0 2.6
Amyl Acetate (iso) 21.6 (1) 1.0
Amyl Alcohol (n) 29.6 1.2
Amyl Alcohol (iso) 29.6 1.2
Benzene 36.8 (1) 1.4
Butyl Acetate (n) 24.8 1.7
Butyl Alcohol (n) 35.2 1.4
Butyl Cellosolve 24.8 1.1
Cellosolve 33.6 1.8
Cellosolve Acetate 23.2 1.7
Cyclohexnone 31.2 (1) 1.1
1,1 Dichloroethylene 42.4 5.9
1,2 Dichloroethylene 42.4 9.7
Ethyl Acetate 32.8 2.5
Ethyl Alcohol 55.2 4.3
Ethyl Lactate 28.0 (1) 1.5
Methyl Acetate 40.0 3.1
Methyl Alcohol 80.8 7.3
Methyl Cellosolve 40.8 2.5
Methyl Ethyl Ketone 36.0 1.8
Methyl n-Propyl Ketone 30.4 1.5
Naphtha (VM&P)
(76 deg. Naphtha)
22.4 0.9
Naphtha (100 deg. Flash)
Safety Solvent -
Stoddard Solvent
23.2 1.0
Propyl Acetate (n) 27.2 2.8
Propyl Acetate (iso) 28.0 1.1
Propyl Alcohol (n) 44.8 2.1
Propyl Alcohol (iso) 44.0 2.0
Toluene 30.4 1.4
Turpentine 20.8 0.8
Xylene (o) 26.4 1.0
   Footnote(1) At 212 deg. F (100 deg. C).
Clean fresh air, free of contamination from adjacent industrial exhaust systems, chimneys, stacks, or vents, shall be supplied to a spray booth or room in quantities equal to the volume of air exhausted through the spray booth.
Where the air supply to a spray booth or room is filtered, the fan static pressure shall be calculated on the assumption that the filters are dirty to the extent that they require cleaning or replacement.
The rating of filters shall be governed by the test data supplied by the manufacturer of the filter. A pressure gage shall be installed to show the pressure drop across the filters. This gage shall be marked to show the pressure drop at which the filters require cleaning or replacement. Filters shall be placed or cleaned whenever the pressure drop across them becomes excessive or whenever the air flow through the face of the booth falls below that specified in Table D-57.7.
Means for heating make-up air to any spray booth or room, before or at the time spraying is normally performed, shall be provided in all places where the outdoor temperature may be expected to remain below 55 deg. F. (12.77 deg. C.) for appreciable periods of time during the operation of the booth except where adequate and safe means of radiant heating for all operating personnel affected is provided. The replacement air during the heating seasons shall be maintained at not less than 65 deg. F. (18.33 deg. C.) at the point of entry into the spray booth or spray room. When otherwise unheated make-up air would be at a temperature of more than 10 deg. F. below room temperature, its temperature shall be regulated as provided in section 3.6.3 of ANSI Z9.2-1960.
As an alternative to an air replacement system complying with the preceding section, general heating of the building in which the spray room or booth is located may be employed provided that all occupied parts of the building are maintained at not less than 65 deg. F. (18.33 deg. C.) when the exhaust system is in operation or the general heating system supplemented by other sources of heat may be employed to meet this requirement.
No means of heating make-up air shall be located in a spray booth.
Where make-up air is heated by coal or oil, the products of combustion shall not be allowed to mix with the make-up air, and the products of combustion shall be conducted outside the building through a flue terminating at a point remote from all points where make-up air enters the building.
Where Make-up air is heated by gas, and the products of combustion are not mixed with the make-up air but are conducted through an independent flue to a point outside the building remote from all points where make-up air enters the building, it is not necessary to comply with paragraph (h)(7)(iv)(F) of this section.
Where make-up air to any manually operated spray booth or room is heated by gas and the products of combustion are allowed to mix with the supply air, the following precautions must be taken:
The gas must have a distinctive and strong enough odor to warn workmen in a spray booth or room of its presence if in an unburned state in the make-up air.
The maximum rate of gas supply to the make-up air heater burners must not exceed that which would yield in excess of 200 p.p.m. (parts per million) of carbon monoxide or 2,000 p.p.m. of total combustible gases in the mixture if the unburned gas upon the occurrence of flame failure were mixed with all of the make-up air supplied.
A fan must be provided to deliver the mixture of heated air and products of combustion from the plenum chamber housing the gas burners to the spray booth or room.
Where a spray booth or room receives make-up air through self-closing doors, dampers, or louvers, they shall be fully open at all times when the booth or room is in use for spraying. The velocity of air through such doors, dampers, or louvers shall not exceed 200 feet per minute. If the fan characteristics are such that the required air flow through the booth will be provided, higher velocities through the doors, dampers, or louvers may be used.
Spray booths or spray rooms are to be used to enclose or confine all spray finishing operations covered by this paragraph (h). This paragraph does not apply to the spraying of the exteriors of buildings, fixed tanks, or similar structures, nor to small portable spraying apparatus not used repeatedly in the same location.
This paragraph applies to all operations involving the immersion of materials in liquids, or in the vapors of such liquids, for the purpose of cleaning or altering the surface or adding to or imparting a finish thereto or changing the character of the materials, and their subsequent removal from the liquid or vapor, draining, and drying. These operating include washing, electroplating, anodizing, pickling, quenching, dying, dipping, tanning, dressing, bleaching, degreasing, alkaline cleaning, stripping, rinsing, digesting, and other similar operation.
Except where specific construction specifications are prescribed in this section, hoods, ducts, elbows, fans, blowers, and all other exhaust system parts, components, and supports thereof shall be so constructed as to meet conditions of service and to facilitate maintenance and shall conform in construction to the specifications contained in American National Standard Fundamentals Governing the Design and Operation of Local Exhaust Systems, Z9.2-1960.
Open-surface tank operations shall be classified into 16 classes, numbered A-1 to D-4, inclusive.
Hazard potential is an index, on a scale of from A to D, inclusive, of the severity of the hazard associated with the substance contained in the tank because of the toxic, flammable, or explosive nature of the vapor, gas, or mist produced there from. The toxic hazard is determined from the concentration, measured in parts by volume of a gas or vapor, per million parts by volume of contaminated air (p.p.m.), or in milligrams of mist per cubic meter of air (mg./m(3)), below which ill effects are unlikely to occur to the exposed worker. The concentrations shall be those in 1926.55 or other pertinent sections of this part.
The relative fire or explosion hazard is measured in degrees Fahrenheit in terms of the closed-cup flash point of the substance in the tank. Detailed information on the prevention of fire hazards in dip tanks may be found in Dip Tanks Containing Flammable or Combustible Liquids, NFPA No. 34-1966, National Fire Protection Association. Where the tank contains a mixture of liquids, other than organic solvents, whose effects are additive, the hygienic standard of the most toxic component (for example, the one having the lowest p.p.m. or mg/m(3)) shall be used, except where such substance constitutes an insignificantly small faction of the mixture. For mixtures of organic solvents, their combined effect, rather than that of either individually, shall determine the hazard potential. In the absence of information to the contrary, the effects shall be considered as additive. If the sum of the ratios of the airborne concentration of each contaminant to the toxic concentration of that contaminant exceeds unity, the toxic concentration shall be considered to have been exceeded. (See Note A to paragraph (i)(2)(v) of this section.)
Hazard potential shall be determined from Table D-57.9, with the value indicating greater hazard being used. When the hazardous material may be either a vapor with a threshold limit value (TLV) in p.p.m. or a mist with a TLV in mg/m(3), the TLV indicating the greater hazard shall be used (for example, A takes precedence over B or C; B over C; C over D).

Note A:

(c1 ÷ TLV1) ÷ (c2 ÷ TLV2)+(c3 ÷ TLV3;... (cN ÷ TLVN)1


c = Concentration measured at the operation in p.p.m.


Hazard potential Toxicity group
Gas or
Flash point in
degrees F. (C.)
A 0-10 0-0.1
B 11-100 0.11-1.0 Under 100
C 101-500 1.1-10 100,200
D Over 500 Over 10 Over 200
Rate of gas, vapor, or mist evolution is a numerical index, on a scale of from 1 to 4, inclusive, both of the relative capacity of the tank to produce gas, vapor, or mist and of the relative energy with which it is projected or carried upwards from the tank. Rate is evaluated in terms of
The temperature of the liquid in the tank in degrees Fahrenheit;
The number of degrees Fahrenheit that this temperature is below the boiling point of the liquid in degrees Fahrenheit;
The relative evaporation of the liquid in still air at room temperature in an arbitrary scale -- fast, medium, slow, or nil; and
The extent that the tank gases or produces mist in an arbitrary scale -- high, medium, low, and nil. (See Table D-57.10, Note 2.) Gassing depends upon electrochemical or mechanical processes, the effects of which have to be individually evaluated for each installation (see Table D-57.10, Note 3).
Rate of evolution shall be determined from Table D-57.10. When evaporation and gassing yield different rates, the lowest numerical value shall be used.

Rate Liquid temperature,
deg. F (C)
Degrees below
boiling point
1 Over 200 (93.33) 0-20 Fast High.
2 150-200 (65.55-93.33) 21-50 Medium Medium
3 94-149 (34.44-65) 51-100 Slow Low.
4 Under 94 (34.44) Over 100 Nil Nil.

     Footnote(1) In certain classes of equipment, specifically vapor degreasers, an internal condenser or vapor level thermostat is used to prevent the vapor from leaving the tank during normal operation. In such cases, rate of vapor evolution from the tank into the workroom is not dependent upon the factors listed in the table, but rather upon abnormalities of operating procedure, such as carryout of vapors from excessively fast action, dragout of liquid by entrainment in parts, contamination of solvent by water and other materials, or improper heat balance. When operating procedure is excellent, effective rate of evolution may be taken as 4. When operating procedure is average, the effective rate of evolution may be taken as 3.
     Footnote(2) Relative evaporation rate is determined according to the methods described by A. K. Doolittle in Industrial and Engineering Chemistry, vol. 27 p. 1169, (3) where time for 100-percent evaporation is as follows: Fast: 0-3 hours; Medium: 3-12 hours; Slow: 12-50 hours; Nil: more than 50 hours.
     Footnote(3) Gassing means the formation by chemical or electrochemical action of minute bubbles of gas under the surface of the liquid in the tank and is generally limited to aqueous solutions.
Class is determined by two factors, hazard potential designated by a letter from A to D, inclusive, and rate of gas, vapor, or mist evolution designated by a number from 1 to 4, inclusive (for example, B.3).
Where ventilation is used to control potential exposures to workers as defined in paragraph (i)(2)(iii) of this section, it shall be adequate to reduce the concentration of the air contaminant to the degree that a hazard to the worker does not exist. Methods of ventilation are discussed in American National Standard Fundamentals Governing the Design and Operation of Local Exhaust Systems, Z9.2-1960.
Control velocities shall conform to Table D-57.11 in all cases where the flow of air past the breathing or working zone of the operator and into the hoods is undisturbed by local environmental conditions, such as open windows, wall fans, unit heaters, or moving machinery.
All tanks exhausted by means of hoods which do not project over the entire tank, and in which the direction of air movement into the hood or hoods is substantially horizontal, shall be considered to be laterally exhausted. The quantity of air in cubic feet per minute necessary to be laterally exhausted per square foot of tank area in order to maintain the required control velocity shall be determined from Table D-57.12 for all variations in ratio of tank width (W) to tank length (L). The total quantity of air in cubic feet per minute required to be exhausted per tank shall be not less than the product of the area of tank surface times the cubic feet per minute per square foot of tank area, determined from Table D-57.12.
For lateral exhaust hoods over 42 inches (1.06 m) wide, or where it is desirable to reduce the amount of air removed from the workroom, air supply slots or orifices shall be provided along the side or the center of the tank opposite from the exhaust slots. The design of such systems shall meet the following criteria:
The supply air volume plus the entrained air shall not exceed 50 percent of the exhaust volume.
The velocity of the supply airstream as it reaches the effective control area of the exhaust slot shall be less than the effective velocity over the exhaust slot area.

Required minimum
control velocity,
f.p.m. (from
Table D-57.11)
C.f.m. per sq. ft. to maintain required minimum
velocities at following ratios (tank width (W)/
tank length (L)(1),(2)
0.0-0.09 0.1-0.24 0.25-0.49 0.5-0.99 1.0-2.0
Hood along one side or two parallel sides of tank when one hood is
against a wall or baffle(2).
Also for a manifold along tank centerline(3).
50 50 60 75 90 100
75 75 90 110 130 150
100 100 125 150 175 200
150 150 190 225 260 300
Hood along one side or two parallel sides of free standing tank not
against wall or baffle.
50 75 90 100 110 125
75 110 130 150 170 190
100 150 175 200 225 250
150 225 260 300 340 375

   Footnote(1) It is not practicable to ventilate across the long
dimension of a tank whose ratio W/L exceeds 2.0.
   It is undesirable to do so when W/L exceeds 1.0. For circular tanks
with lateral exhaust along up to 1/2 the circumference, use W/L=1.0; for over one-half the circumference use W/L=0.5.
    Footnote(2) Baffle is a vertical plate the same length as the tank,
and with the top of the plate as high as the tank is wide. If the exhaust hood is on the side of a tank against a building wall or close to it, it is perfectly baffled.
   Footnote(3) Use W/2 as tank width in computing when manifold is along centerline, or when hoods are used on two parallel sides of a tank.
   Tank Width (W) means the effective width over which the hood must
pull air to operate (for example, where the hood face is set back from the edge of the tank, this set back must be added in measuring tank width). The surface area of tanks can frequently be reduced and better control obtained (particularly on conveyorized systems) by using covers extending from the upper edges of the slots toward the center of the tank.
The vertical height of the receiving exhaust hood, including any baffle, shall not be less than one-quarter the width of the tank.
The supply airstream shall not be allowed to impinge on obstructions between it and the exhaust slot in such a manner as to significantly interfere with the performance of the exhaust hood.
Since most failure of push-pull systems result from excessive supply air volumes and pressures, methods of measuring and adjusting the supply air shall be provided. When satisfactory control has been achieved, the adjustable features of the hood shall be fixed so that they will not be altered.
All tanks exhausted by means of hoods which project over the entire tank, and which do not conform to the definition of enclosing hoods, shall be considered to be overhead canopy hoods. The quantity of air in cubic feet per minute necessary to be exhausted through a canopy hood shall be not less than the product of the control velocity times the net area of all openings between the bottom edges of the hood and the top edges of the tank.
The rate of vapor evolution (including steam or products of combustion) from the process shall be estimated. If the rate of vapor evolution is equal to or greater than 10 percent of the calculated exhaust volume required, the exhaust volume shall be increased in equal amount.
All tanks exhausted by means of hoods which
Project over the entire tank;
Are fixed in position in such a location that the head of the workman, in all his normal operating positions while working at the tank, is in front of all hood openings; and
Are completely enclosed on at least two sides, shall be considered to be exhausted through an enclosing hood.
The quantity of air in cubic feet per minute necessary to be exhausted through an enclosing hood shall be not less than the product of the control velocity times the net area of all openings in the enclosure through which air can flow into the hood.

Class Enclosing hood Lateral
Canopy hood[2]
One open
Two open
Three open
Four open
B-1 and A-2 100 150 150 Do not use Do not use
A-3[2], B-1, B-2,
and C-1
75 100 100 125 175
A-3, C-2, and
65 90 75 100 150
B-4[2], C-3, and
50 75 50 75 125
A-4, C-4, D-3[3],
and D-4[4]
Footnote(1) See Table D-57.12 for computation of ventilation rate.
Footnote(2) Do not use canopy hood for Hazard Potential A processes.
Footnote(3) Where complete control of hot water is desired, design as next highest class.
Footnote(4) General room ventilation required.
Wherever spraying or other mechanical means are used to disperse a liquid above an open-surface tank, control must be provided for the airborne spray. Such operations shall be enclosed as completely as possible. The inward air velocity into the enclosure shall be sufficient to prevent the discharge of spray into the workroom. Mechanical baffles may be used to help prevent the discharge of spray. Spray painting operations are covered by paragraph (h) of this section.
Tank covers, foams, beads, chips, or other materials floating on the tank surface so as to confine gases, mists, or vapors to the area under the cover or to the foam, bead, or chip layer; or surface tension depressive agents added to the liquid in the tank to minimize mist formation, or any combination thereof, may all be used as gas, mist, or vapor control means for open-surface tank operations, provided that they effectively reduce the concentrations of hazardous materials in the vicinity of the worker below the limits set in accordance with paragraph (i)(2) of this section.
The equipment for exhausting air shall have sufficient capacity to produce the flow of air required in each of the hoods and openings of the system.
Two or more operations shall not be connected to the same exhaust system where either one or the combination of the substances removed may constitute a fire, explosion, or chemical reaction hazard in the duct system. Traps or other devices shall be provided to insure that condensate in ducts does not drain back into any tank.
The exhaust system, consisting of hoods, ducts, air mover, and discharge outlet, shall be designed in accordance with American National Standard Fundamentals Governing the Design and Operation of Local Exhaust Systems, Z9.2-1960, or the manual, Industrial Ventilation, published by the American Conference of Governmental Industrial Hygienists 1970. Airflow and pressure loss data provided by the manufacturer of any air cleaning device shall be included in the design calculations.
The capacity required in paragraph (i)(7)(i) of this section shall be obtained when the airflow producing equipment is operating against the following pressure losses, the sum of which is the static pressure:
Entrance losses into the hood.
Resistance to airflow in branch pipe including bends and transformations.
Entrance loss into the main pipe.
Resistance to airflow in main pipe including bends and transformations.
Resistance of mechanical equipment; that is, filters, washers, condensers, absorbers, etc., plus their entrance and exit losses.
Resistance in outlet duct and discharge stack.
The required airflow shall be maintained at all times during which gas, mist, or vapor is emitted from the tank, and at all times the tank, the draining, or the drying area is in operation or use. When the system is first installed, the airflow from each hood shall be measured by means of a pitot traverse in the exhaust duct and corrective action taken if the flow is less than that required. When the proper flow is obtained, the hood static pressure shall be measured and recorded. At intervals of not more than 3 months operation, or after a prolonged shutdown period, the hoods and duct system shall be inspected for evidence or corrosion or damage. In any case where the airflow is found to be less than required, it shall be increased to the required value. (Information on airflow and static pressure measurement and calculations may be found in American National Standard Fundamental Governing the Design and Operation of Local Exhaust Systems, Z9.2-1960, or in the manual, Industrial Ventilation, published by the American Conference of Governmental Industrial Hygienists.)
A volume of outside air in the range of 90 percent to 110 percent of the exhaust volume shall be provided to each room having exhaust hoods. The outside air supply shall enter the workroom in such a manner as not to be detrimental to any exhaust hood. The airflow of the makeup air system shall be measured on installation. Corrective action shall be taken when the airflow is below that required. The makeup air shall be uncontaminated.