Spray room safety

[Tom Hoffman]

Is the following setup safe for a finishing/spray room?

• Partition off an 8x10 room in my shop, totally enclose it with paneling or drywall. One wall is a shop exterior wall.
• Nothing electrical in the room
• Install a window to the outside on the one shop exterior wall
• Install a fan on one of the walls interior to the shop, but exterior to spray room, blowing filtered air into the room, with exhaust going out the window. (kind of like a whole house fan, but in reverse)
• Spray oil based finishes via HVLP keeping the turbine outside of the spray room (run the hose through a sealed hole in the wall.

The idea is to avoid the need for explosion proof fans, light switches, etc. and just use ambient light from the window.

Am I nuts?

[Joe Chritz]

If you are going to set up a room for spraying solvent base finishes you really should set it up according to specs. Woodweb has a finishing section and it is most pros. There is lots of information on spray booths and the like.

A lot depends on the volume of the material you are spraying. If you are spraying a 1/2 quart of pre-cat lacquer the set up is probably perfectly safe. If you are spraying for 3 hours it will probably make a smoking hole.

You could avoid the problem and go waterbase and have all the benefits with none of the negatives.

The only non waterbase product I spray is shellac in the form of sealcoat. That is only as a barrier and the amount sprayed is very small comparitively speaking.

Joe

[Jack Briggs]

Tom,


So far you've described my spraybooth. 8'x10' stud framed and 1/2" drywalled. I sealed all drywall joints with caulking and duct tape. A 14"x20" filer frame for incoming air and a 20"x25" framed for outgoing air. Filter frames hold 2"x20"x25" fiberglass filters for overspray, and I've got an exposion-proof motor with a 12" aluminum (non-sparking) 4-blade fan. I got the motor and blade from Grainger several years ago for a little over $200. I built a plenum for the fan which ducts outside thour 12" snap-lock ducting, sealed with dust tape. The fan will move 1100 CFM, which is close to twice the volume of the room per minute.

I strongly advise getting the explosion-proof motor, as it's cost is not that much more and you would want it sometime in the future to be able to spray lacquer, shellac, etc.



Cheers,

[Rob Cunningham]

Tom,
I don't feel that ambient light from one window is going to give you enough light for finishing. Spray rooms are usually well lit. Also, I think it would be better to have the fan in the window pulling the overspray out,through a filter, and filtered air in. Blowing air into the room is not necessarily going to force the overspray out the window. It will probably just blow it around and all over your finished pieces.
As Joe said, WB would be a good solution. Then you can have good lighting etc, without having to worry about fire/explosions.You still need to wear a respirator though.
If you are going to stick with solvent based finishes you should really follow code and have an approved spray booth.

[Rick Christopherson]

In a spray booth where the operator is working in the same environment as the spray, then you really have little to worry about except for small isolated pockets. If you check the MSDS sheets for the products you will use, you will see that the Lower Explosive Limit (LEL) is near or above the Immediately Dangerous to Life and Health (IDLH) limit. What this means is that before you ever reach an explosive concentration in your shop, you are either dead already, or passed out on the floor. Most people would stop spraying by that point.

You certainly don't want your water heater in the same space, but generally speaking, explosion proof design is not a big deal in a home shop. As long as air is moving in the space, isolated pockets of high concentration are going to be rare, and even then, down in the lower corners.

[Bob Slater]

How do you think this would work ? I have a 2HP Dust Gorilla in a separate room. I run a duct with a blast gate into the room with the hazardous goods, then re direct the exhaust through a wood stove chimney that is not being used. It seems to me any explosive elements would not be in contact with any sparks, motor , electrical, and the CFM moved would be substantial.