// CODE SNIPPET
1910.94(c)(6) Velocity and Air Flow Requirements
JUMP TO FULL CODE CHAPTER
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 G-10 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 G-10 when measured upstream or above the object being sprayed.
NOTES:
Operating conditions for objects completely inside booth |
Crossdraft, f.p.m. |
Airflow velocities, f.p.m. | |
Design | Range | ||
Electrostatic and automatic air-less operation contained in booth without operator. |
Negligible. | 50 Large booth | 50-75 |
Air-operated guns, manual or automatic |
Up to 50 | 100 small booth 100 large booth |
75-125 75-125 |
Air-operated guns, manual or automatic |
Up to 100 | 150 small booth 150 large booth |
125-175 125-175 |
200 small booth | 150-250 |
- 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.
- Crossdrafts can be eliminated through proper design and such design should be sought. Crossdrafts in excess of 100 fpm (feet per minute) should not be permitted.
- 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.
- 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 must be used by employees that has been approved by the NIOSH under 42 CFR part 84 for the material being sprayed.
Where downdraft booths are provided with doors, such doors shall be closed when spray painting.
In addition to the requirements in paragraph (c)(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 G-11. 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) divided by LEL
Using toluene as the solvent.
Footnote(1) At 212 deg. F.
Example: To determine the lower explosive limits of the most common solvents used in spray finishing, see Table G-11. 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) divided by LEL
Using toluene as the solvent.
- LEL of toluene from Table G-11, column 2, is 1.4 percent.
- Cubic feet of vapor per gallon from Table G-11, column 1, is 30.4 cubic feet per gallon.
- Dilution volume required =
4 (100 - 1.4) 30.4 divided by 1.4 = 8,564 cubic feet. - 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. |
Lower explosive limit in percent by volume of air at 70 deg. F. |
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 |
Cyclohexanone | 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 Acetate | 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 |
Related Code Sections
1910.94(c)(6) Occupational Health and Environmental Control, Velocity and Air Flow Requirements
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 ...
OSHA 1910 General Industry > G Occupational Health and Environmental Control > 1910.94 Ventilation > 1910.94(c) Spray Finishing Operations > 1910.94(c)(6) Velocity and Air Flow Requirements
1910.94(c)(7)(ii) Occupational Health and Environmental Control,
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 ...
OSHA 1910 General Industry > G Occupational Health and Environmental Control > 1910.94 Ventilation > 1910.94(c) Spray Finishing Operations > 1910.94(c)(7) Make-Up Air > 1910.94(c)(7)(ii)
1910.252(c)(3)(i) Welding, Cutting, and Brazing, Hoods
Freely movable hoods intended to be placed by the welder as near as practicable to the work being welded and provided with a rate of air-flow ...
OSHA 1910 General Industry > Q Welding, Cutting, and Brazing > 1910.252 General Requirements > 1910.252(c) Health Protection and Ventilation > 1910.252(c)(3) Local Exhaust Hoods and Booths > 1910.252(c)(3)(i) Hoods
1910.252(c)(3) Welding, Cutting, and Brazing, Local Exhaust Hoods and Booths
with a rate of air-flow sufficient to maintain a velocity in the direction of the hood of 100 linear feet (30 m) per minute in the zone of welding when ...
OSHA 1910 General Industry > Q Welding, Cutting, and Brazing > 1910.252 General Requirements > 1910.252(c) Health Protection and Ventilation > 1910.252(c)(3) Local Exhaust Hoods and Booths
1910.94(c)(7) Occupational Health and Environmental Control, Make-Up Air
If the fan characteristics are such that the required air flow through the booth will be provided, higher velocities through the doors, dampers ...
OSHA 1910 General Industry > G Occupational Health and Environmental Control > 1910.94 Ventilation > 1910.94(c) Spray Finishing Operations > 1910.94(c)(7) Make-Up Air