A practical guide to NFPA 33 and the other codes that shape a paint booth project: NEC Article 516, OSHA 1910.107, the fire code, EPA 6H, and CARB and California air district rules.
At a Glance
The core fire-safety standard for spray finishing. It covers how the spray area is built (walls, doors and ceilings of noncombustible or limited-combustible material), exhaust ventilation and how it is interlocked with the spray equipment, electrical classification in and around the spray area, automatic fire protection, filter maintenance, and housekeeping. Fire marshals and insurers rely on it heavily when they review a booth.
The National Electrical Code sets the hazardous-location classification of the spray area and the space around booth openings, and the wiring and equipment allowed in each zone. That is why booth lighting is Class I Division 1 or Division 2 rated and why motors, controls and panels are placed outside the classified area or rated for it.
Federal workplace-safety rules for spray finishing with flammable and combustible materials. 1910.107 covers booth construction, electrical and ignition sources, ventilation, storage and handling of liquids, and fire protection. 1910.94(c) covers ventilation of spray finishing operations. Respiratory protection (1910.134) and hazard communication rules also apply to painters.
The International Fire Code, adopted in California as the California Fire Code, has a chapter on flammable finishes that local fire departments enforce for spray booths, spray rooms and mixing areas. It addresses booth construction and materials, ventilation, fire protection, and the quantity of flammable liquids kept in the area. Local amendments are common.
The federal air-toxics rule (NESHAP) for paint stripping and miscellaneous surface coating at area sources. Shops that spray coatings containing target metals (chromium, lead, manganese, nickel or cadmium) on metal or plastic parts, and motor vehicle refinishers, generally must spray in a filtered booth or enclosure with exhaust filters rated at least 98% capture efficiency, use HVLP or equivalent spray guns, train and certify painters, and file EPA notifications.
In California, local air districts issue the permits to construct and operate a spray booth and enforce VOC limits on coatings and cleanup solvents, while CARB sets statewide measures. Expect the district to ask for booth and filter specifications, coating usage and SDS data before the booth runs. See our California paint booth permitting guide.
Last reviewed October 2026, NFPA 33 2024 edition. Your local authority having jurisdiction (AHJ) may still enforce an earlier edition, so confirm the adopted edition with your fire marshal or building department before design starts.
NFPA 33 is organized by topic. These plain-language summaries explain what each part of the standard covers. They are not the code text; always work from the edition your AHJ enforces. Tap a topic to open it.
This part covers what a spray booth or spray room is built from and where it can sit. Walls, ceilings and doors are expected to be noncombustible or limited-combustible, interior surfaces smooth so overspray residue can be cleaned off, and the booth separated from other operations by clear space or a fire-rated wall.
NFPA 33 (5.3.2) requires sheet-metal booth walls and ceilings to be at least 1.2 mm (about 18 gauge) for single-wall panels, or at least 0.9 mm (about 20 gauge) per sheet for double-wall panels. Aluminum isn’t allowed for walls, ceilings or structural members (5.1.3).
It also covers access and exits for operators, panels and view windows, and how multiple booths connected together are treated.
This part defines the hazardous (classified) locations in and around a spray area and limits what electrical equipment can be used there. It works together with NEC (NFPA 70) Article 516.
Beyond wiring, it addresses other ignition sources: open flames, hot surfaces, sparks from tools, static electricity (grounding and bonding of the booth, equipment, containers and parts) and lighting fixtures, which must either be rated for the location or sit outside it behind sealed panels.
This part requires mechanical exhaust that keeps flammable vapor well below the level that could ignite, and that captures overspray. It covers interlocks between the exhaust fan and spray equipment, make-up air, exhaust duct construction and routing to the outside, and keeping the exhaust system clean.
This part limits how much flammable and combustible liquid can be kept in and near the spray area, and covers approved containers, mixing rooms, transfer and pumping systems, and grounding and bonding while liquids are poured or pumped.
This part covers flash-off areas, spray booths that also bake (spray/bake or heated booths) and drying equipment near spray areas. The main ideas: heating cannot run unless ventilation is proven, spraying and heated cure modes are controlled so they do not overlap unsafely, and heaters are kept from igniting vapors or residue.
Separate industrial ovens are generally covered by NFPA 86, which your AHJ may also apply.
Powder coating has its own requirements because airborne powder is a combustible dust. The focus is keeping powder concentration in the booth well below the level that could ignite, grounding parts and equipment, controlling ignition sources and, for automated electrostatic systems, fast fire detection that shuts the system down.
Booth materials for powder-only booths can differ from liquid booths when the AHJ approves. See our powder coating booths.
The topics booth buyers ask about most, explained in our own words. Section numbers and exact values come from the code edition your AHJ enforces. Tap a topic to open it.
A spray booth is normally separated from other operations either by clear open space around it (NFPA 33 commonly cites 3 ft) or by a wall, floor or ceiling assembly with at least a 1-hour fire-resistance rating. Booths built and connected as one installation are generally not treated as “other operations” for each other.
Construction is noncombustible or limited-combustible, with smooth interior surfaces so residue can be cleaned off. Plan the booth location with your AHJ early, because separation affects floor layout.
Exhaust ventilation must keep the concentration of flammable vapor below 25% of the lower flammable limit (LFL), the lowest concentration at which a vapor can ignite. In practice the booth is sized so normal spraying stays far below that.
NFPA 33 and NEC Article 516 classify the spray area as a hazardous location. The inside of the booth, its exhaust plenum and ducts are typically Class I, Division 1: flammable vapor can be present during normal operation, so only equipment rated for Division 1 belongs there.
A defined area just outside the booth openings is typically Class I, Division 2: vapor is only expected if something goes wrong. The size of that zone depends on the booth type, its openings and whether the exhaust is interlocked with the spray equipment. Lighting is often mounted outside the booth behind sealed glass panels so the fixtures stay out of the most hazardous zone.
Spray areas need automatic fire protection covering the booth and its exhaust plenum and ducts. Automatic sprinklers designed to NFPA 13 are the most common approach. Other approved automatic systems (for example dry chemical, carbon dioxide or clean agent systems designed to their own NFPA standards) can be used where the AHJ approves them.
Fire protection is usually designed by a fire protection contractor and approved by the AHJ and often your insurer. Tell us early what system is planned so the booth layout accounts for heads, nozzles and detection.
NFPA 33 is written for spray application of flammable or combustible materials. Operations that may fall outside its scope include spraying materials that are not flammable or combustible, outdoor spray operations, and occasional small-scale work such as touch-up with small portable equipment or aerosol cans not used repeatedly in the same place.
These exceptions are narrow and depend on the edition and local amendments. Even when NFPA 33 does not apply, the fire code, OSHA and air district rules usually still do. Your AHJ makes the final call.
The fastest permit reviews happen when the booth buyer has a clear equipment package and a complete description of coating operations. Before submitting, collect the booth drawings, airflow data, utility requirements, coating types, SDS information, and fire protection strategy.
PFS designs and manufactures industrial finishing systems in California and supports buyers with equipment documentation, booth configuration guidance, AMU planning, replacement filters, and service records that can support local review.
The full guide and checklist as a printable PDF to share with your team, fire marshal or insurer.
Download the PDFNFPA 33 is commonly used by AHJs when spray application involves flammable or combustible materials. The exact requirement depends on local code adoption, coating chemistry, occupancy, and facility use.
No. NFPA 33 focuses on fire and spray application safety. California facilities may also need review by South Coast AQMD, BAAQMD, San Joaquin Valley APCD, SDAPCD, CARB, or another local air district.
PFS can provide equipment documentation, service records, filter information, and technical information that supports AHJ, insurer, or permit review. Final approval remains with the local authority.
NFPA 33 is a consensus fire-safety standard adopted through fire and building codes. OSHA 1910.107 is a federal workplace-safety regulation for spray finishing. They cover many of the same topics, and a booth project should satisfy both.
Lighting and electrical equipment inside and near the spray area must suit its hazardous-location classification under NEC Article 516, typically Class I Division 1 or 2. That is why booth light fixtures are rated and often serviced from outside the booth.
It can, if you spray coatings containing chromium, lead, manganese, nickel or cadmium on metal or plastic parts, or refinish motor vehicles. Check your coatings’ SDS and the rule’s applicability criteria, or ask your air district.
In California, most spray booths need a permit from the local air district before construction or operation, along with fire and building department approval. See our California permitting guide for details.
In most cases, yes. NFPA 33 requires automatic fire protection for the spray area, including the exhaust plenum and ducts. Automatic sprinklers designed to NFPA 13 are the most common choice; other approved automatic systems such as dry chemical or clean agent can be used where your AHJ approves them.
NFPA 33 commonly calls for either clear space around the booth (3 ft is the figure usually cited) or a wall, floor or ceiling assembly with at least a 1-hour fire-resistance rating between the booth and other operations. Confirm the requirement in the edition your AHJ enforces.
Division 1 is where flammable vapor can be present in normal operation, typically the booth interior, exhaust plenum and ducts. Division 2 is where vapor is only expected if something goes wrong, typically a defined area just outside the booth openings. Equipment must be rated for the zone it sits in.
NFPA 33 covers drying and curing in or next to spray areas, such as flash-off zones and heated spray/bake booths, including interlocks so heat cannot run without ventilation. Separate industrial ovens are generally covered by NFPA 86. Your AHJ decides which apply.
Yes. NFPA 33 has requirements specific to powder coating, which treat airborne powder as a combustible dust: keeping powder concentration low, grounding, controlling ignition sources and, for automated electrostatic systems, fire detection that shuts the system down.
NFPA 33 does not set one schedule for every shop; it requires that overspray residue not be allowed to build up in the booth, exhaust plenum and ducts, and that dirty filters be replaced and disposed of safely. How often depends on how much you spray. Use non-sparking tools for cleaning and follow the filter manufacturer’s change point on your pressure gauge.
NFPA 33 (5.3.2) requires sheet-metal booth walls and ceilings to be at least 1.2 mm (about 18 gauge) for single-wall panels, or at least 0.9 mm (about 20 gauge) per sheet for double-wall panels. Aluminum isn’t allowed for walls, ceilings or structural members (5.1.3).
