How do National Fire Protection Association codes apply to your spray booth?
Open Front Spray Booths: Without an exhaust fan interlock a Class 1, Division 2 safety zone extends10 ft. from the opening of the booth – an interlock between the fan and the spray guns cuts the safety zone to 5 ft. With or without an interlock, a 3-ft. safety zone is needed around the top of the opening.
I'm sure that you have heard this at one time or another: "The code says …," "The ruling is …," or "According to …," and while these sayings may be familiar to us, the applicable codes and rulings may not be, especially the National Fire Protection Association or NFPA 33. This standard for spray applications including flammable, combustible materials, is a collection of fire safety methods and procedures that when followed keep us safe and healthy.
Many people are afraid of rules, especially government sponsored rules. What we should fear is the results of accidents that are caused from not knowing effective safety rules and practices.
Organizing the Hazards
Fires and the potential for fires by electrical ignition are organized into "Class" and "Division." If you've ever read the nomenclature tag on a fire extinguisher you will find the extinguisher's effect corresponds to the "Class" of fire it is made to combat.
There are three classifications with which body shops must deal:
Class I: Liquid-volatile, flammable liquid (paint, solvent, reducers, etc.);
Class II: Dust-combustible dust not normally in the air, in quantities sufficient to cause combustion, especially when in the vicity of electrical apparatus (sanding dust); and
Class III: Fibers-the presence of ignitable fibers in the air (fiberglass).
"Division" is the severity and location with which the class of material is being eliminated:
Division 1: "Ground Zero" or the source or origin of the hazard;
Division 2: "Fallout Area" or a given distance away from the source but still in sufficient quantities to be considered as a hazard.
How close to walls and partitions can a spray booth be located?
The spray booth must have a clear space of at least 3 ft. on all sides, and the space not being used for storage. All parts of the booth must be accessible for cleaning. But there are some exceptions.
The spraybooth can be directly placed against an interior wall, partition, floor or ceiling assembly that has a fire resistance rating of less than one hour. It is good practice to check with your fire marshal first on this before proceeding. Also, the spray booth can be closer than 3 ft. to any wall or partition that is constructed of non-combustible material and so long as the booth can be maintained and cleaned.
Keeping a clear space around the booth is just good housekeeping. There is little chance for any spray painting being done inside the booth to have any affect on items outside of the booth. The wisdom of the ruling is that we have a natural tendency to store items in these spaces. Paint, solvent, thinner or reducers are sure to find their way into these spaces.
Should any electrical components be inside the spray booth?
No. Remember that inside the spray booth, when using a spraygun, you have a Class I, Division 1 condition. The last thing you want is the ignition of sprayed material. To provide electricals in a Class I, Division 1 condition that meets code (NFPA 70 and the National Electrical Code) is extremely expensive, usually far in excess of the cost of the booth itself. Installing an "explosion-proof" electrical fixture with conventional (non-explosion proof) wiring and accessory items does not meet code. So do yourself a favor and keep all electricals out of the spray booth.
What do the rules say about electricals outside of the spray booth?
The ruling for this situation has expanded within the last several years, and now covers booths with and without exhaust fan interlock, which is when the compressed air supply to the booth is controlled by the exhaust fan. When the fan is not turned on and running, there is no compressed air available to the sprayguns in the booth. There are prescribed areas outside of the spray booth openings that are designated as Class I, Division 2 locations. Any electrical fixture or component located in this given area must meet the Class I, Division 2 or "vapor-proof" requirements. Any fixture and / or component beyond those prescribed areas can be "standard" or "open" type.
What are recommended and acceptable lighting fixtures?
The only fixtures that are discussed in NFPA 33 are approved, fluorescent tube-type light fixtures as well as their proper mounting technique. Use lighting fixtures that are made for spray booth applications. Do not use nor install standard shop or general-purpose light fixtures inside the spray booth. Do not allow yourself to be talked into using "explosion-proof" fixtures inside of the booth.
What are the NFPA 33 rules in regards to exhaust fans?
Prevention of fires is still the goal. In a nutshell, NFPA 33 simply says that moving parts, such as blades and impellers, in the air stream that contains flammable vapors must be of non-ferrous material. They should be non-sparking. Note: Fans are not rated by nor listed as being in compliance with NFPA 33. Fan manufacturers refer to their own Air Movement and Control Association (AMCA) standard. AMCA Standard 99-0401-86 covers the requirements and classifications of fan construction for spray booths. It lists construction method types A, B and C, which are nearly word-for-word from the NFPA 33 requirements.
Which style of electric motor is best?
NFPA 33 clearly states that the motor is not to be in the stream of contaminated air, which means outside of the booth and stack. Thus it is in an environment that is deemed safe for personnel. An open drip-proof (ODP) or totally enclosed fan cooled style of motor will work. You do not need an explosion-proof style of motor. By definition, if there is an environment around the spray booth that is explosive, then the booth is in the wrong place and employees are being placed in danger.
Mix Room The mix room has restrictions similar to a spray booth, including electrical classifications, and qualifies as being in Class I, Division 2 condition. The following are NFPA 33 conditions for a mix room:
Must have same construction as the spray booth;
Not to exceed 150 sq.ft. of floor space;
Be able to contain a liquid spill;
Have mechanical ventilation of 1 cu. ft. per minute (cfm) for each square foot of floor area, or 150 cfm maximum;
Automatic fire suppression system as the spray booth;
Portable fire extinguisher.
Up to 60 gal. in the booth and up to 120 gal. in the mix room and spray booth combination. The maximum allowable amount of paint storage requires the largest permitted mix room of 150 sq. ft., 10 ft. by 15 ft. for example, to be located at least 6 ft. from the spray booth. Vestibule-connected or not, this size and location of a mix room will permit up to 300 gal. of storage. Vestibule connecting of mix room to booth or booth to mix room to another booth or any combination is good practice.
Fire Suppression All types of automatic sprinkler systems are indicated in NFPA 33, and no specific systems recommended. This is left up to the approval of the authority who has jurisdiction. Please remember that the local fire marshal is still the final authority. You must have a fire suppression system for your equipment. The sprinklers will be protected from paint over-spray in the booth and from unfiltered paint in the exhaust chamber and stack. They will be covered with cellophane bags that are 0.003 in. thick or less. Thin paper bags will work, too. Your fire protection supplier and installer is your best source for what to install for your given area and situation.
Vehicle Undercoating Where in the shop can undercoating and body lining jobs be performed?
NFPA 33 is not crystal clear on this. It states that the area for this operation has adequate natural or mechanical ventilation-a jurisdiction call by the authority having jurisprudence. There are four criteria to meet:
No open flames or spark-producing equipment to be within 20 ft. of the operation;
No drying or curing apparatus to be within 20 ft .;
No solvent for cleaning with a flash point of less than 100 degrees F (37.8 degrees C);
The coating or lining material shall: a.) Be no more hazardous than UL Class 30-40 when tested in accordance with UL 340; b.) Have no solvent or component with a flash point below 100 degrees F (37.8 degrees C); and c.) Consist only of Class IIIB liquids, and have no organic peroxide catalyst. If any of the above is not met, then the undercoating and body lining must be done in an approved finishing application area.
Prep stations are one of the most recent items now covered by NFPA 33. The size of these areas depend on whether the exhaust fan is interlocked with the compressed air system. The area required is much larger than for a spray booth. The curtains are to be non-combustible and are to be closed during spray painting. No more than one gallon of material is to be sprayed during an eight-hour period. The area inside of the curtains is to be considered as Class I, Division 1 hazardous.
When considering the purchase of new finishing equipment, insist on booths and equipment that have been designed and manufactured according to NFPA 33 requirements. Reputable booth manufacturers will be willing to state this in writing, if they do not already do so in their literature. For those who won't-beware!