Custom Spray Booths and
Finishing Systems

NFPA 33 FAQS

General Compliance

What is NFPA 33, and who needs to comply with it?

NFPA 33 is the national standard for spray application using flammable or combustible materials. Any facility that operates spray booths, spray rooms, or spray areas for industrial coating applications must comply with NFPA 33. This includes aerospace manufacturers, automotive facilities, furniture manufacturers, and any industrial operation using spray-applied coatings.

Is NFPA 33 legally required?

While NFPA 33 itself is a standard, not a law, it is typically adopted and enforced by local authorities having jurisdiction (AHJ), OSHA regulations, insurance companies, and building codes. Non-compliance can result in fines, shutdown orders, insurance issues, and increased liability in case of accidents.

How often is NFPA 33 updated?

NFPA 33 is typically revised every 3-5 years. The current edition is 2018, with updates expected periodically. It’s important to verify which edition your local jurisdiction has adopted, as they may not immediately adopt the newest version.

Booth Design & Construction

What’s the minimum distance required between a spray booth and other operations?

Spray booths must be separated by either 3 feet of clear space OR a partition with a 1-hour fire resistance rating. Multiple connected spray booths are considered a single operation and don’t require separation from each other.

Ventilation & Air Flow

Can I recirculate air from my spray booth back into the plant?

For liquid spray operations, recirculation is only allowed if you meet ALL requirements, including: particulate filters, vapor monitoring below 25% of the lower flammable limit, automatic shutdown systems, and AHJ approval. Powder coating booths have more flexibility for recirculation with proper filtration and monitoring.

Do exhaust fans need to run continuously?

Yes, ventilation must operate during all spray operations AND continue afterward long enough to exhaust vapors from drying coatings. Automatic spray equipment must be interlocked so spraying cannot occur without ventilation running.

What type of fans are required?

Fans must be spark-resistant and constructed of materials appropriate for the materials being sprayed. The fan motor must be located outside the airstream or be rated for the hazardous location classification.

Electrical & Safety Systems

What electrical equipment can I use inside the spray booth?

All electrical equipment inside the booth must be rated for Class I, Division 1 hazardous locations. This includes lights, switches, outlets, and any control equipment. Equipment within 3 feet of booth openings must be Class I, Division 2 rated.

Do I need explosion-proof lighting?

Not necessarily. Lights separated from the spray area by approved glass panels and serviced from outside can be standard-rated. However, any lights inside the classified area must meet hazardous location requirements.

Is fire suppression required?

Fire suppression requirements depend on your local codes and the specific materials being sprayed. Automatic sprinkler systems are often required, and portable fire extinguishers must always be readily available.

Materials & Storage

How much paint can I store near my spray booth?

If your mixing room is within 6 feet of the spray area, the combined total cannot exceed 120 gallons. If separated by more than 6 feet, you can store up to 300 gallons in the mixing room and 60 gallons in the spray area.

What are nitrocellulose applications, and why do they require special handling?

Nitrocellulose lacquers are fast-drying coatings used on furniture, musical instruments, and some automotive finishes. They require special handling because overspray can spontaneously ignite. NFPA 33 requires either water-wash booths or daily cleaning of dry filters and baffles for these materials.

Can I spray different types of coatings in the same booth?

Generally, yes, but you cannot use the same filters for materials that may spontaneously ignite when mixed (like nitrocellulose and oil-based materials). Some material combinations may require complete cleaning between applications.

Powder Coating Booths

Are powder coating booths subject to different requirements?

Yes, Chapter 15 of NFPA 33 specifically addresses powder coating with unique requirements for electrical grounding, dust collection, explosion protection, and the advantage of being able to recirculate filtered air back into the plant.

Do I need explosion venting for powder coating?

Depending on the size and design of your powder system, explosion protection per NFPA 68 may be required. This typically involves explosion venting or suppression systems for dust collectors and recovery systems.

Maintenance & Operations

How often do I need to change booth filters?

NFPA 33 doesn’t specify exact intervals for standard operations, but filters must be changed when they become loaded enough to affect booth performance. For nitrocellulose applications, daily filter changes are required. Always follow manufacturer recommendations and maintain proper airflow.

Who is the “Authority Having Jurisdiction” (AHJ)?

The AHJ is typically your local fire marshal, building inspector, or OSHA representative who has the legal authority to enforce codes and approve installations. Requirements can vary by location, so it’s important to identify and work with your specific AHJ.

Where can I get a complete copy of NFPA 33?

The complete NFPA 33 standard can be purchased from NFPA.org. Free access to view (but not print or download) the standard is also available on their website with registration.