NFPA 33-2018 Standard for Spray Application Using Flammable or Combustible Materials.
11.3.9 Safeguards such as booths, fencing, railings, interlocks, or other means shall be placed about the equipment or incor‐ porated therein so that they, either by their location or charac‐ ter or both, ensure that a safe separation of the process is maintained. 11.3.10 Signs shall be conspicuously posted for the following purposes: (1) To designate the process zone as dangerous with regard to fre and accident (2) To identify the grounding requirements for all electrically conductive objects in the spray area, including persons (3) To restrict access to qualifed personnel only 11.3.11 All insulators shall be kept clean and dry. 11.4 Incendive Equipment. Spray equipment that is not considered to be nonincendive shall comply with 11.4.1 and 11.4.2. 11.4.1 Conveyors, hangers, and application equipment shall be arranged so that a minimum separation of at least twice the sparking distance is maintained between the workpiece or material being sprayed and the electrodes, electrostatic atomiz‐ ing heads, or charged conductors. Warnings defning this safe distance shall be provided. 11.4.2* The high-voltage elements shall be automatically de- energized rapidly enough to prevent an arc in the event the clearance between the objects or material being coated and the electrodes or electrostatic atomizing heads falls below that specifed in 11.4.1. 11.5 Listing and Approval of Equipment. Spray equipment shall be listed or shall meet the requirements of 11.5.1 or 11.5.2. 11.5.1 Spray equipment that was installed prior to December 31, 1997, shall be listed or approved. 11.5.2 This requirement shall not apply to automatic electro‐ static spray equipment protected in accordance with Sections 9.7 or 9.9.
12.5 Grounding. 12.5.1* The handle of the spray gun shall be electrically connected to ground by a conductive material. It shall be constructed so that the operator, in normal operating position, is in electrical contact with the grounded handle by a resistance of not more than 10 6 ohms (1 megohm) to prevent buildup of a static charge on the operator’s body. Signs indicating the necessity for grounding persons entering the spray area shall be conspicuously posted. 12.5.2 All electrically conductive objects in the spray area, except those objects required by the process to be at high volt‐ age, shall be electrically connected to ground with a resistance of not more than 1 megohm (10 6 ohms). This requirement shall apply to containers of coating material, wash cans, guards, hose connectors, brackets, and any other electrically conduc‐ tive objects or devices in the area. This requirement also shall apply to any personnel who enter the area. 12.5.3 Conductive objects or material being coated shall be electrically connected to ground with a resistance of not more than 10 6 ohms (1 megohm). Areas of contact shall be sharp points or knife edges, where possible, and those areas of contact shall be protected from overspray, where practical. 12.5.4 Highly resistive objects (i.e., surface conductivity between 10 8 and 10 11 ohms per square) that exhibit a surface voltage below 2500 volts, as measured using a nonloading kilo‐ voltmeter and when subjected to coronal current not less than that expected in the application process, shall be considered adequately grounded.NFPA 33 pdf download.