Spray Application, Dipping, and Coating

A spray booth is a purpose-built classified location. Inside the booth and a defined space around the openings is treated as Division 1 or 2 depending on ventilation, and the residue that builds on every surface is its own fire load. Lighting has to be behind sealed glass, and equipment is kept out of the direct spray zone wherever possible.

The interlock with ventilation is the rule I never let anyone defeat. If the exhaust fan is not running, the spray equipment should not energize, because a booth without airflow fills with mist in seconds. I also stay on top of overspray buildup, since a thick coat of dried paint on a fixture is just fuel waiting on a spark.

When it applies

Article 516 covers spray application, dipping, and coating, wherever atomized paint or solvent vapor makes an ignitable cloud. It classifies the booth interior and a defined zone around openings as hazardous, and ties the electrical system to ventilation, so equipment cannot run when the exhaust fans are down.

Common mistakes

• Placing ordinary lighting, receptacles, or motors inside the classified zone instead of listed hazardous-location equipment.
• Ignoring the interlock that stops spraying when ventilation fails, that link is a core part of the article.
• Letting overspray build up on fixtures and conduit, that residue is fuel and it defeats the enclosure rating.

In the field

I verify the fan-to-spray interlock actually works, not just that it is wired, before I sign off a booth. Ventilation is what keeps the vapor below the ignitable range, so a booth that can spray with the fans off is an explosion waiting for a timer.