Explosion-proof fans

      Building a safe spray booth to eliminate the risk of explosions. January 24, 2001

Question
What is an explosion-proof fan? I am building a small spray booth, and all the notes I have seen demand such a fan.

Forum Responses
The electrical motor on an explosion-proof fan is contained, so no sparks can possibly blow your spray room up. They are more expensive than a standard motor but necessary when spraying solvent-based stain and finish.



Also, the fan is connected to the motor via belt. To build a spray booth on your own, you have to get permits from the EPA and the fire department. You almost must have explosion-proof lights and an explosion-proof electric panel and wiring connecting the spray both.


You don't always need to go with explosion-proof motors and lights. Depending on the mounting location of the fan, you can use a totally enclosed fan-cooled motor.

In most cases you can use sealed and gasketed light fixtures in booths--it depends on how you mount them and where they are mounted. The lights that come on booths from Devilbiss, Binks, etc, are sealed and gasketed fixtures, called class 1, division 2, as compared to class 1, division 1, which are explosion-proof. The quality of light you get from a sealed and gasketed light is much better than the incandescent explosion-proof light. You can get explosion-proof fluorescents, but they’re expensive.



I'm also setting up a (safe-as-possible) spray room, but I am not using an explosion proof fan.

My room is 10' x 12' with an 8' ceiling. The fan is a 14" axial fan with a TEFC motor (direct drive). The fan is rated at 2000 CFM and I will have a 48 x 24 filter panel for inlet air. I can add a further 24 x 24 panel if needed, and I will fabricate a filter panel to catch overspray before it gets to the fan.

The size and shape of the exhaust hood will be based on the size of the filter media (an air filter supplier suggests using roll material, cheap and easy to replace as it gets plugged).

I have two sets of basic fluorescent 4 tube fixtures in the room, and the switch is outside. I also have a supplied fresh air system, which uses a helmet.



I too am using a TEFC motor in a positive pressure airtight booth. I have the fan mounted outside the booth near the top, which keeps the motor and electrical connections out of the booth. The fan blows air into the booth, which raises the pressure inside. The air and fumes escape through four large vents near the floor, which is where the fumes collect.

This is the safest and cheapest way to light the booth: Cut holes in the wall of the booth like windows. Mount glass over the holes from the outside, sealing them perfectly, and then mount lights outside, so they shine in through the glass.



The comments below were added after this Forum discussion was archived as a Knowledge Base article (add your comment).

When we speek about ventilators used in explosible atmospheres, there is a new Europeen regulation, the ATEX 94/9/CE that gives an obligation to the plant to define zones of explosible atmosphere. In Zone 0 (continual presence of explosible atmosphere inside the fan), the only ventilator allowed is a ventilator that stands 10 bars explosion pressure, equipped on both sides with flame arresters to stop explosion propagation, and being certified and tested in explosion by a notified body. This is the only way to sell a Zone 0 ventilator in the Europeen Union.



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