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NFPA 33: Standard for Spray Application Using Flammable or Combustible Materials
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What is NFPA 33?
NFPA 33: Document Scope

1.1* Scope. A.1.1 The risk to life and property because of the fire and explosion hazards of spray application of flammable and combustible materials varies depending on the arrangement and operation of the particular process and on the nature of the material being sprayed. The principal hazards addressed in this standard are those of the materials being sprayed: flammable and combustible liquids and combustible powders, as well as their vapors, mists, and dusts, and the highly combustible deposits and residues that result from their use. Properly designed, constructed, and ventilated spray areas are able to confine and control combustible residues, dusts, or deposits and to remove vapors and mists from the spray area and discharge them to a safe location, thus reducing the likelihood of fire or explosion. Likewise, accumulations of overspray residues, some of which are not only highly combustible but also subject to spontaneous ignition, can be controlled. The control of sources of ignition in spray areas and in areas where flammable and combustible liquids or powders are handled, together with constant supervision and maintenance, is essential to safe spray application operations. The human element requires careful consideration of the location of spray application operations and the installation of fire extinguishing systems so that the potential for spread of fire to other property and damage to property by extinguishing agent discharge is reduced. 1.1.1* This standard shall apply to the spray application of flammable or combustible materials, as herein defined, either continuously or intermittently by any of the following methods: (1) Compressed air atomization (2) Airless or hydraulic atomization (3) Electrostatic application methods (4) Other means of atomized application A.1.1.1 Refer to Figure A.1.1.1 for assistance in determining whether NFPA 33 applies to a particular spray application process. ****INSERT FIGURE HERE**** FIGURE A.1.1.1 Decision Tree — Does NFPA 33 Apply? 1.1.2 This standard shall also apply to the application of flammable or combustible materials, as herein defined, either continuously or intermittently by any of the following methods: (1) Fluidized bed application methods (2) Electrostatic fluidized bed application methods (3) Other means of fluidized application 1.1.3 This standard shall also apply to spray application of water-borne, water-based, and water-reducible materials that contain flammable or combustible liquids or that produce combustible deposits or residues. 1.1.4* This standard shall not apply to spray operations that use less than 1 L (33.8 fl oz) of flammable or combustible liquid in any 8-hour period. A.1.1.4 There are many industrial applications that involve routine use of small quantities of flammable or combustible liquids (e.g., coatings, lubricants, adhesives) on a regular or periodic basis. An example would be touch-up of manufactured articles using aerosol containers or small, portable spray application equipment. The intent of this provision is to allow such use without having to comply with the requirements of NFPA 33. 1.1.5* This standard shall not apply to spray application processes or operations that are conducted outdoors. A.1.1.5 This standard does not cover spray application operations that are conducted outdoors on buildings, bridges, tanks, or similar structures. These situations occur only occasionally for any given structure and overspray deposits are not likely to present a hazardous condition. Also, the space where there might be an ignitible vapor–air or dust–air mixture is very limited due to atmospheric dilution. 1.1.6* This standard shall not apply to the use of portable spraying equipment that is not used repeatedly in the same location. A.1.1.6 The occasional use of small portable spray equipment or aerosol spray containers is not likely to result in hazardous accumulations of overspray. Therefore, such operations are not within the scope of this standard. The following safeguards, however, should be observed: (1) Adequate ventilation should be provided at all times, particularly where spray application is conducted in relatively small rooms or enclosures. (2) Spray application should not be conducted in the vicinity of open flames or other sources of ignition. Either the spray operation should be relocated or the source of ignition should be removed or turned off. (3) Containers of coating materials, thinners, or other hazardous materials should be kept tightly closed when not actually being used. (4) Oily or coating-laden rags or waste should be disposed of promptly and in a safe manner at the end of each day’s operations, due to the potential for spontaneous ignition. (5) The same fundamental rules for area cleanliness and housekeeping that are required for industrial spray application operations should be observed. 1.1.7 This standard shall not apply to the use of aerosol products in containers up to and including 1 L (33.8 oz) capacity that are not used repeatedly in the same location. (See A.1.1.6.) 1.1.8 This standard shall not apply to the spray application of noncombustible materials. 1.1.9 This standard shall not apply to the hazards of toxicity or to industrial health and hygiene. (See 1.2.2.)

This standard provides requirements to mitigate fire and explosion hazards of spray application processes that use flammable or combustible materials.

Official document scope
What does NFPA 33 address?

Criteria apply to automated and hand-held spray application processes, as well as specific requirements for electrostatic spray systems. NFPA 33 also includes specific requirements for powder coating processes, vehicle undercoating and body lining, limited finishing workstations, and hand lay-up and spray fabrication of glass fiber-reinforced plastics. Included are rules covering the construction of spray rooms, spray booths, and mixing rooms, along with their electrical, ventilation, fire protection systems. Also included are rules for drying and curing processes, operations, and maintenance.

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