Reprinted with permission from NFPA 33-2011, Standard for Spray Application Using Flammable or Combustible Materials, Copyright © 2010, National Fire Protection Association, Quincy, MA. This reprinted material is not the complete and official position of the NFPA on the referenced subject, which is represented only by the standard in its entirety. The following is section 15 from NFPA 33:
Chapter 15 Powder Coating
15.1* Scope. This chapter shall apply to processes in which combustible dry powders are applied.
15.2 General. The installation and use of powder coating application apparatus shall comply with the requirements of this chapter and also shall comply with the applicable requirements of all other chapters. 15.3 Applicability. Section 15.4 through Section 15.10 are general and shall apply to all methods of powder coating application.
Section 15.11 through Section 15.13 shall apply to the specific method indicated therein.
15.4 Location. Powder coating operations shall be confined to enclosures that are located in accordance with Chapter 4.
15.5 Protection. Powder coating operations shall be protected in accordance with Chapter 9.
15.6 Enclosures. Powder shall be confined by conducting coating operations within one of the following: (1) A completely enclosed, ventilated room of noncombustible or limited-combustible construction with smooth surfaces designed to prevent accumulation of powder and to facilitate cleaning (2) A ventilated spray booth meeting the requirements of Section 5.1 through Section 5.5, and having enclosed, ventilated containers (tanks, bins, etc.)
15.7 Electrical and Other Sources of Ignition.
15.7.1 Electrical utilization equipment and other sources of ignition shall meet both the requirements of Chapter 6 of this standard and Articles 500, 502, 504, and 516 of NFPA 70, National Electrical Code, as applicable. 15.7.2 Where the object or material being coated is preheated in an oven, the controls shall be set so that the surface temperature of the object or material does not come within 28°C (50°F) of the autoignition temperature of the powder used. 15.7.3 All electrically conductive objects in the spray area, except those objects required by the process to be at high voltage, shall be electrically connected to ground with a resistance of not more than 1 megohm (106 ohms), as measured with an instrument that applies at least 500 volts to the circuit being evaluated. This requirement shall also apply to any personnel who enter the area.
15.8 Ventilation, Dust Collection, and Explosion Protection. See Annex C.
15.8.1* Ductwork. Where non-deposited, air-suspended powder (powder overspray) is conveyed by ductwork to a recovery system, sufficient airflow shall be provided in the ductwork to maintain the powder concentration in the ductwork at not more than 50 percent of the minimum explosive concentration (MEC) of the powder in use. Exhaust equipment shall bear an identification plate stating the ventilation rate for which it was designed. Exception: Where, by design, the coating operation is conducted at an exhaust duct concentration above 50 percent of the MEC, listed explosion suppression equipment shall be provided. 15.8.1.1 The manufacturer of the powders being used shall provide the MEC of those powders for the purposes of proper design of the exhaust system.
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