Hi,
I’m building a spraybooth out of a cabinet, using 70cfm exhaust bath fan.
Does it matter where the fan (the suck-in with a filter) is located? I’m puting mine in the middle at the bottom of a back wall of a cabinet. I think gravity should help the airflow.
Or should I move the fan closer to the top?
On the back wall is a reasonably good location for the filter, but a bath fan isn’t rated for ignitable vapor removal, so have your fire suit and a good extinguisher at the ready.[;)]
Spraybooths typically use shaded pole fans, or alternately some kind of arrangement where the motor is not in the path of volatile vapors and paint particles, since some motors can spark.
Are acrylics ignitable vapour?
If I’ll cover the motor with some metal housing, or the motor will overheat?
The paints are not but what you thin them with such as iso alcohol is.
On that note though I think people are far too cautious about this subject. I have never heard of any airbrusher having a fire from their paintbooth and every paintbooth I have seen does not use a certified, “explosion proof” blower. You would have to be in an enclosed room with stagnant air to get the small amount of thinner in your airbrush to ignite. Nothing wrong with being cautious but let’s not get overboard here.
I didn’t think dispensing advice on the cautionary side (especially where fire is concerned) was the equivalent of “going overboard”. I think erring on the side of caution allows one to live a long life. I have heard of two accounts of how someone’s home made spraybooth ignited by using sub-standard removal fans. That’s enough data for me. No need to repeat that experiment in the comfort of my own home! Look, if you’re going to go through the trouble of building something, why not just build it right?
I cannot seem to find any specialized fans in my area…
Will something like this work?
The motor seems to be covered…
Well Mark, caution if fine but I stand by what I said. None of the commercial made spray booths for modeling have “explosion proof” motors so if you want to err on caution then buy the expensive explosion proof motors to be on the safe side. They are quite pricey by the way.
When you “hear” stories of someone’s booth catching on fire you never know the details so that is really not a valid argument IMHO. As long as the booth’s motor is operating properly and the room is not filled with fumes the chance of a fire is basically 0. If you choose to believe otherwise that is fine but I don’t think these booths are near as dangerous as some would have you believe.
This is beginning to look like an argument for argument’s sake…
Look, Mike, one of those stories I mentioned came from a guy (a very good modeler) who I used to work with years ago. He came in one day without his eyelashes. Lucky that’s all he lost! He was not known to be a liar. Would you now say my point is still not valid, IYHO?
Now please tell me exactly where I stated that “all booth motors must be “explosion proof” motors”. I said “shaded pole or other arrangement, etc…”. I’m not quite sure how you got on this kick about “explosion proof” motors, but I didn’t start that one.
Yes, a good booth motor is more costly than your average bathroom fart fan, but so what? Shall we just dispense with safety, because it costs a few dollars more? Most suitable fans can be bought for under one hundred dollars. Not that bad, really, in the big picture.
Look, it’s just common sense to know that any time one places an arcing, sparking electrical device into the direct path of volatile fumes/particulates, there is a potential for ignition. Minimal, in most cases, but it’s there. What one chooses to do with that fact is their business, I suppose.
So hey, roll those dice!
As I said Mark it all depends on the circumstances. I have a friend that I mentioned before who used a big box fan in a shop that sprayed lacquer through that fan and never had a fire so as I said, it all depends on the user.
Sorry Mark but if you are going to talk about what is safe you have to talk about explosion proof motors right? Just because a motor is “shaded pole” doesn’t mean squat as far as being explosion proof. If you can provide proof otherwise I am all ears bro.
You are not talking about what I mentioned Mark. Explosion proof motors are more expensive than that.
True! So why not err on the side of caution and buy a motor that is guaranteed to be explosion proof? If you are going to press the question then why not follow it?
Are you actually, in a roundabot way, admitting that indeed one can start a fire with a spray booth?
Well it’s not just the user. It’s several factors, combined, just so, to produce the perfect storm. My point is, it has happened. Why would I lie to you, Mike? That’s not the Christian way.
By the way, your friend is a walking hazard. I’m fairly certain that OSHA would not approve of his work ethic!
Mike, what are you talking about? Shaded pole motors, I am told (by a guy at Grainger), are brushless, and don’t produce sparks. Brushless motors are recommended when used with volatile compounds. You can use a squirrel cage arrangement, where just the fan, and NOT the motor, is in the path of fumes, and this should be just fine. I am under no obligation whatsoever to demand an “explosion proof” motor, it is not always needed.
DISCLAIMER: I am not an expert, nor authority, on electric motors!
That’s because there’s no need to talk about it. It is not always required, so this is a moot point, really.
Because, again, they’re not always required for sufficient safety.
Now is there anything else you needed to vent about? (A little spray booth humor there!)
My apologies for being argumentative on the forum Mark.
I agree with you in that he should use a shaded pole squirrel cage blower motor as that is what all the companies that make spray booths sell. They are not rated as explosion proof as I said but as I have been saying all along the chance of a fire is very slim unless you do something really stupid. I guess it is better to err on the side of caution because some people are just not that bright sometimes. [D)] [(-D]
Not saying that anyone here falls into that category mind you as that was not my intent.
PM sent, Mike.
No, that kind of fan wouldn’t work and would be pretty hard to connect to a booth. This is the kind of fan you should be looking for.
The centrifugal (“squirrel cage”) fan that Bill linked you to is your best choice, IMHO. Axial fans, such as the bath fan you referenced in your OP can also be used provided you can get one rated high enough to give you the cfm necessary for good particulate and vapor capture.
The 70cfm figure you quote isn’t nearly enough, unless your booth face is 6" X 6"…
Fans should be chosen based on what your booth size is going to be, not as the initial first step. Ideally, a fan should be able to provide about 100fpm (capture velocity) at the booth face and give you about 2,000 fpm out the terminal exhaust end. That 100 fpm figure has to be based on the booth face area.
As has been argued above, safety is a definite consideration. The entire purpose of a spray booth is to reduce the risk of fire during spraying operations. Equally important is the reduction in exposures of personnel to organic vapors and particulates. While I don’t believe the risk for fire is high when using an airbrush, the added benefit of a shaded pole fan cannot be overstated. Arguments may abound concerning risk associated with airbrush spraying, but I think there’s a tendency to forget the high probability (based partly on the frequency) of a modeler pulling out the old rattle can. I think risk increases fairly dramatically in that instance–both from a fire and an exposure standpoint. I also think it must be understood that I’m referring to risk using those booths with fans that are providing adequate airflow (~100fpm) as a standard. In those booths using underpowered fans (and in this forum there’s been a dump truck full of 'em over the years), I think risk becomes unacceptable. Maybe y’all think I’m blowing smoke; that’s OK, I don’t mind. After almost 30 years in the safety and health field, I’ve developed a rather conservative approach.
Gip
I wish Gip would visit more often. I would much rather just go 
than risk saying something wrong!
I’m one of the guys who contributed to that dump truck full he alludes to. My homemade booth uses a kitchen fan, and certainly isn’t the best example. It’s too big, the fan is in the wrong position and is too small, but when I use it my wife can’t tell I’m painting (acrylics only), and that is worth its weight in gold. But I would never risk using a rattle can in it! I only look dumb!
One day I’ll build a smaller downdraft using the right kind and size of fan, and when I do, I’ll slap a “Gip Approved” sticker on it! [:D]
I agree Gip is da man! [(-D]
Thanks guys!
Finally, found a squirrel cage fan (the last one). Wasn’t easy…
Picking up a few of them tomorrow, depending on their productivity, they seem rather small.
My booth is 20"X16", I guess around 150-200 cmf should do it.
By the way… How is it possible to tell fan’s cfm? I hope there’s some markings on it.
Another thing, does the power of airbrush compressor matter for determining the required fan’s cfm?
I’ve got this little toy Testors blue compressor. And I’ll never use rattle cans indors anyway.
The fan is way too small. These look like computer cooling fans, given their size. The fact that no cfm rating is provided should cause red flags to go up. I’d stay away from them. Go to Grainger’s or Dayton’s web site and research their fans.
Given those dimensions you need at least 225 cfm to provide 100fpm capture velocity. I would be looking for something in the 250-300 cfm range.
Usually, manufacturers’ literature lists a fan’s specifications. Again, try Grainger or Dayton as a source.
One has nothing to do with the other. And never say “never”. [swg]
Gip
OK, I asked my friend Scooter about this subject and he told me I was free to post his reply here. This man knows what he is talking about and airbrushed for probably 40 years. He was also instrumental in getting the T&C Vega airbrush on the market years ago.
From the email he sent me:
I am not sure what he meant by a “fart fan” so I guess I will have to ask him. [(-D]
Thanks Mike!
And thanks to your friend Scooter!
I saved the letter for later[:)], but this booth that I’m doing is build into a computer armoire I got in walmart. Sort of putting all my hobby stuff in one closet. I live in an apartment so I’ve got to make everything as compact as possible. When I’ll get a house - the proper booth will be constructed.
I got a fan named “Orix”, it’s a japanese fan, solid metal [:)]. No cfm is listed but when I pluged it in - blows like crazy. I’ll install one in the back wal, if it will not be enough, I’ll add one more.