According to the National Fire Protection Association, the most common causes of fire in spray painting operations are a result of improper separation of the paint booth from other areas using ignitable equipment--welders, grinders, cutters--and electrical equipment. NFPA Standard 33 outlines the safety requirements for paint booths and is included in the Occupational Health and Safety Administration (OSHA) standards. These standards must be followed closely to avoid fire- and breathing-related injuries at work.
According to the National Fire Protection Association and OSHA, paint booths must be completely separated from all other operations and located at least 20 feet from any combustible materials. Both also require paint booths to have a separate, approved sprinkler system, a fire rating of at least two hours and be built according to certain construction standards.
Paint booths must be made of concrete, masonry or supported and secured steel. Another non-combustible material, like aluminium, is acceptable for low-volume operations. All materials used in constructing paint booths must be non-combustible including those used in the connecting air supply. The booths must also be designed for safe, easy cleaning and so that fumes will sweep toward the exhaust. More specifics on paint booth construction are found in OSHA standards 1910.94(c) and 1910.107.
All electrical and combustible materials inside the booth and within 20 feet of the booth are covered under OSHA standards. Only fixed lighting enclosed in protective panels and portable lamps approved for hazardous Class I locations may be used in spray booths. This includes all lighting outside of the booth within 20 feet. All open flames, heat and spark producing equipment must be kept 20 feet from the booth unless separated by a partition. Inside the booth, electrical wiring and equipment must also be approved for hazardous Class I, Division 1 locations. Wiring and electrical equipment outside the booth but within 20 feet must be approved for hazardous Class I, Division 2 locations. Finally, all metal parts of the spray booth must be properly grounded.
Paint booths must be equipped with a mechanised ventilation system to remove harmful fumes and airborne residues from the booth. Air exhaust may not be recirculated and must be directed away from the booth's air intakes. The exhaust discharge clearances set by OSHA must be followed carefully to prevent fire hazard and harmful fumes. All of the parts of the ventilation system--the independent exhaust, fans, motors, belts and exhaust ducts--must be compliant with OSHA rule 1910.94(c)(5). Adequate ventilation must also be provided for painted items to dry to prevent the build-up of explosive fumes.
Velocity and Air Flow
OSHA standard 1910.94(c)(6) specifies the minimums for air velocities in spray booths according to the specific operation and size of the booth. Refer to OSHA's table G-10 on this standard, when designing the booth. In addition, harmful fumes must be diluted to 25 per cent of their lower explosive limit as presented in the tables under OSHA standard 1910.94(c)(6)(ii) and table G-11. A compliant air-supplied respirator must be provided for workers downwind from the item being sprayed. Doors must be closed during spray painting.
The paint booth must be supplied with new, clean air equal to the amount exhausted from the booth. Any doors that supply this air must be left open during spraying and the velocity may no be more than 200 feet per minute. The air may not be heated from within the booth. More specific regulations for each operation may be found in OSHA standard 1910.94(c)(7).
Baffles and Overspray Collectors
Overspray filters and distribution and baffle plates must be made of non-combustible material, properly installed and located for easy cleaning, inspection and replacement. All collecting tanks and systems must be constructed according to OSHA standard 1910.94(c).