International Fire Code 2021 (IFC 2021)

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About this chapter: Chapter 22 provides requirements that seek to reduce the likelihood of dust explosions by managing the hazards of ignitable suspensions of combustible dusts associated with a variety of operations including woodworking, mining, food processing, agricultural commodity storage and handling and pharmaceutical manufacturing, among others. This chapter provides various requirements to control ignition sources, use properly listed and designed dust collection systems, maintain good housekeeping practices and provide proper training to those involved in these processes. Appropriate standards are referenced to deal with the specific dust hazards.

The equipment, processes and operations involving dust explosion hazards and use or handling of combustible dust shall comply with the provisions of this chapter.


  1. Storage and use of consumer materials in Group B or R occupancies.
  2. Storage and use of commercially packaged materials in Group M occupancies.
  3. Materials displayed in original packaging in Group M occupancies and intended as building materials or for personal or household use.
  4. Storage of sealed containers of combustible dust at facilities not associated with an operation that uses, handles or generates combustible dust.
  5. Materials stored or used in farm buildings or similar occupancies intended for on-premises agricultural purposes.
Permits shall be required for combustible dust-producing operations as set forth in Section 105.5.
The maximum dust layer on all surfaces, including but not limited to walls, ceilings, beams, equipment, furniture, pipes and ducts, shall not exceed the critical depth layer specified in Table 2203.1. The critical depth layer is permitted to be adjusted for explosion hazard where further evaluated in accordance with one of the following:
  1. Section of NFPA 654.
  2. Section of NFPA 664 for wood flour.
Accumulated combustible dust shall be collected by one of the methods listed in Section 2203.5.
TABLE 2203.1
Wood flour 1/8
All other dusts 1/32

For SI: 1 inch = 25.4 mm.

Dust-producing equipment and dust-handling equipment, including but not limited to vacuums, dust collection systems, dryers, mixers, blenders, separators, conveyors, storage containers, silos or other similar devices, shall be listed and shall be maintained in accordance with the manufacturer's recommended standards.
Signages and markings shall be provided in accordance with Sections 2203.2.1.1 through 2203.2.1.3.
Where dust collection systems and other equipment, systems or system components are provided with deflagration vents, the area within the deflagration vent's discharge area shall be marked in an approved manner.
Signs that read as follows shall be posted near the dust-containing equipment with deflagration vents:
Where dust collection systems and other equipment, systems or system components are provided with deflagration vents, vent closures shall be clearly marked as follows:
Dust-collection and dust-conveying systems shall be in accordance with Sections 2203.3.1 through 2203.3.3.
Dust-collection systems shall be designed to collect dust emissions from dust-producing equipment at the point of generation. Dust-collection systems shall be in accordance with Section 511 of the International Mechanical Code.

Exception: Closed systems using listed equipment and designed in accordance with manufacturer's recommendations and specifications, where cleanouts are provided in accordance with Section 2203.3.3.

Heating, ventilation, and air conditioning (HVAC) systems shall not be used as the means to collect dusts from localized sources.
Dust collectors shall be located outside of buildings.


  1. Dust collectors inside buildings complying with Section 511 of the International Mechanical Code.
  2. Wet-type dust collectors specifically listed for the type of dust conveyed shall be permitted inside buildings where in accordance with the manufacturer's instructions and specifications.
  3. Dust collectors designed to specific NFPA standards listed in Table 2205.1 for the specific type of dust conveyed.
The minimum velocities within ducts used as part of the dust collection system shall be in accordance with Table 2203.3.1.2.
TABLE 2203.3.1.2
Fine light dust such as cotton, lint and wood flour (100 mesh and under) 2,000
Dry dust such as fine rubber molding powder 2,500
Average dust such as sawdust, grinding dust and coal dust 3,500
Heavy dust such as metal turnings, including aluminum and magnesium powder 4,000

For SI: ;1 foot per minute = 0.00508 m/s.

Plastic, fiberglass, other nonconductive ducts, duct liners or pipes shall not be used as part of ducts and conveying systems. Ductwork utilizing a combustible lining shall be permitted only in high-impact areas and where approved. Flexible hose shall be permitted if designed and installed in accordance with the following requirements:
  1. Manufactured of static dissipative construction.
  2. Used only for connections and isolation purposes.
  3. Limited to 18 inches (457 mm) in length.
  4. Properly grounded.
Openings in enclosed equipment and conveyors shall be provided to allow access to all parts of the equipment and conveyors to permit inspection, cleaning, maintenance and the effective use of portable fire extinguishers or hose streams. Cleanouts for ducts used as part of the dust-collection system shall be in accordance with the International Mechanical Code.
Sources of ignition shall be controlled in accordance with Sections 2203.4.1 through 2203.4.9.5.
Classified electrical shall be in accordance with NFPA 70. Electrical motors and electrical components of the equipment shall not be installed in the dust-laden airstream unless listed for Class II, Division 1, locations.
Bonding and grounding is required to minimize accumulation of static electric charge in the following locations:
  1. Dust-producing equipment.
  2. Dust-collection system.
  3. Pneumatic dust-conveying systems conveying combustible dust from one location to another, combustible dust conveyors, piping and conductive components. Conveying systems include transport modes such as railcars, hopper cars, boxcars, tank cars and trucks into which or from which commodities or products are pneumatically conveyed.
  4. Conveying systems using metallic piping.
Hot work and similar spark-producing operations shall not be conducted in or adjacent to combustible dust-producing areas unless precautions have been taken to provide safety. Hot work shall be permitted only in safe, designated areas in accordance with Chapter 35. Hot work is prohibited on equipment that is operating.
Conspicuous signs with the following warning shall be posted in the vicinity of combustible dust-producing areas or in the vicinity of combustible dust use:


In areas where a dust explosion hazard or dust flash fire hazard exists, the temperature (in degrees Celsius) of external surfaces shall be maintained below 80 percent of the lower of the dust-surface ignition temperature or the dust-cloud ignition temperature for worst-case dusts. External surfaces shall include but are not limited to:
  1. Compressors.
  2. Steam, water or process piping.
  3. Ducts.
  4. Conveyors.
  5. Process equipment.
Where steam pipes or hot surfaces occur in dust-producing or dust-handling areas, accumulation of dust on the surfaces shall be minimized by an approved method.

Exception: Drying apparatus listed for the intended use and installed in accordance with the manufacturer's instructions.

Powered industrial trucks used in electrically classified areas shall be listed for such use.
Smoking shall be prohibited in or adjacent to dust-producing or dust-handling areas. "No Smoking" signs complying with Section 310 shall be conspicuously posted in such areas. Smoking shall be permitted only in designated areas.
Spark-producing devices shall not be located within 20 feet (6096 mm) of areas requiring classified electrical unless separated by a permanent partition.
Materials in silos and other large storage piles of particulates prone to self-heating shall be in accordance with Section 9.4.11 of NFPA 652.
Open flames and fuel-fired equipment shall be in accordance with Sections 2203.4.9.1 through 2203.4.9.5.
Production, maintenance or repair activities that have the potential to release or force combustible dust to become airborne shall not be conducted within 35 feet (11 m) of an open flame or pilot flame.
Fuel-fired space heaters drawing local ambient air shall not be located within electrically classified areas. Space-heating appliances in dust-producing or dust-handling areas shall be located where not subject to the accumulation of deposits of combustible dust.
Fuel-fired process equipment shall be listed for its intended use and shall be operated and maintained in accordance with the manufacturer's instructions.
Inspection and maintenance of fuel-fired process equipment shall include verification that significant combustible dust accumulations do not exist within or around the equipment.
In Class II electrically classified locations, heating units shall be provided with a source of combustion air ducted directly from the building exterior or from an unclassified location.
Accumulation of combustible dust on surfaces inside buildings shall be maintained below the critical depth layer in Section 2203.1. Pressurized air or similar methods shall not be used to remove dust from surfaces. Accumulated combustible dust shall be collected by one of the following methods:
  1. Portable vacuum cleaners listed for use in Class II, Group G, Division 1, atmospheres as defined in NFPA 70.
  2. Dust collection systems.
  3. Other approved means that will not place combustible dust into suspension in air.

Exception: Forced-air or similar methods shall be permitted to remove dust in accordance with NFPA 652, NFPA 654 or NFPA 664.

Dust-producing equipment and all associated equipment, including dust-collection equipment, shall be maintained in accordance with the manufacturer's instructions and specifications and applicable codes. The inspection, testing and maintenance program shall include the following, as applicable:
  1. Fire and explosion protection and prevention equipment, as applicable, in accordance with the appropriate NFPA standards.
  2. Dust-control equipment.
  3. Control of potential ignition sources.
  4. Electrical, process and mechanical equipment, including applicable process interlocks.
  5. Lubrication of bearings for dust-collection, dust-handling and dust-producing equipment.
  6. Additional maintenance in accordance with the manufacturer's instructions and specifications for dust-collection, dust-handling and dust-producing equipment.
Records shall be kept of maintenance and repairs performed. The standard operating procedures shall be submitted to the fire code official for review and approval. The written standard operating procedures shall be signed by the person responsible for facility operations.
A written emergency response plan shall be developed for preventing, preparing for and responding to work-related emergencies, including but not limited to fire and explosion. The following information shall be developed into the plan:
  1. Identification of dust hazards.
  2. Identification and location of all utilities to affected areas.
  3. Site plans or floor plans locating utility shutoff controls, including water, gas and power.
  4. The potential for explosion.
  5. Locations of fire-extinguishing equipment compatible with the hazards present.
  6. Any additional information required by the fire code official.
The plans and procedures required in Sections 2203.5, 2203.6 and 2203.7 shall be approved by the fire code official. The plans and procedures shall be reviewed annually and updated as required by process changes. Initial and annual refresher training shall be provided to employees who are involved in operating, maintaining and supervising facilities that handle combustible dust. Initial and annual refresher training shall include:
  1. Workplace hazards.
  2. General orientation, plant diagrams and plant safety rules.
  3. Process description or flowchart.
  4. Equipment operation, safe startup and shutdown, and response to hazard conditions or an incident.
  5. The location and use of all related fire and explosion protection and prevention systems.
  6. Equipment maintenance requirements and practices, including visual inspections of conveyors and ducts.
  7. Housekeeping requirements, including the maintenance of the critical depth layer in Section 2203.1.
  8. Emergency response plans as required in Section 2203.7.
The employer shall maintain records of initial and annual training and review.
Where combustibility or explosivity screening tests are required to analyze the combustible dust as part of compliance with Section 104.8 and Section 414.1.3 of the International Building Code, they shall be in accordance with Section 5.4 of NFPA 652.
Representative samples for the screening test shall be obtained in accordance with Section 5.5 of NFPA 652.
The fire code official is authorized to enforce additional industry- or material-specific provisions of the codes and standards listed in Table 2205.1 to prevent and control dust explosions, as applicable.
TABLE 2205.1
NFPA 61 Standard for the Prevention of Fires and Dust Explosions in Agricultural and Food Processing Facilities
NFPA 68 Standard on Explosion Protection by Deflagration Venting
NFPA 69 Standard on Explosion Prevention Systems
NFPA 70 National Electrical Code
NFPA 77 Recommended Practice on Static Electricity
NFPA 85 Boiler and Combustion System Hazards Code
NFPA 120 Standard for Fire Prevention and Control in Coal Mines
NFPA 484 Standard for Combustible Metals
NFPA 654 Standard for Prevention of Fire and Dust Explosions from the Manufacturing, Processing and Handling of Combustible Particulate Solids
NFPA 655 Standard for the Prevention of Sulfur Fires and Explosions
NFPA 664 Standard for the Prevention of Fires and Explosions in Wood Processing and Woodworking Facilities
If a dust hazard analysis (DHA) is required by the fire code official for new or existing facilities and operations, it shall be in accordance with NFPA 652. The DHA for existing facilities shall be in accordance with Section 7.1.1 of NFPA 652.
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