Paint booth ventilation

[Scott_F]

Just putting the finishing touches on my shop - hope to start banging rivets soon. For wintertime painting/priming, I was thinking of building a paint booth in the corner and would like some thoughts on how much ventilation is required. At first I was thinking a box fan with filter blowing into the booth and a dryer vent exhaust to the outside, but I get the impression that might not move enough air. Would also appreciate any thoughts on blowing air in vs. sucking air out to ventilate booth.

Thanks,
Scott

[Spike]

You might want to start by finding out what the circulation rate is for a professional booth. I bet there is a standard on how fast booths have to replace all of the air. Welcome to the group !!

-- John

[DefiantSix]

You might want to start by finding out what the circulation rate is for a professional booth. I bet there is a standard on how fast booths have to replace all of the air. Welcome to the group !!

-- John

You bet there is a standard. It's called the Uniform Building Code (or ANSI, or something else, depending on your area.)

Generally speaking, for an installation that is expected to meet a government's building code, it'll require equipment capable of 2-3 complete air changes per hour. Calculate the air volume of the space you intend to work in, and compare it to the rating of the equipment (most equipment is rated in Cubic Feet per Minute (CFM) so don't forget to multiply by 60). If the equipment's rating shows that it'll handle the volume 2-3 times in an hour, you've got a winner.

Good Luck!

[LooseNut]

This thread is a little old ... but anyway ... here is one of my favorite, sleeper shop improvements ...

With all due respect Def-Six dude, I think that "Uniform Building Code" spec for 2-3 air changes per hour must be for, like, office space or something. No way can this be for a paint booth! That might be ok for clearing out an ocassional fart, but when the shop air is full of chemicals I can hardley pronounce or spell, I want a little more flow!

I started out, probably like other builders, by hanging one of those box fans in the window. This really didn't cut it.

One day, I thought I wanted to have a really long shelf on the wall. (Proably the day after the wing kit arrived and I noticed a bunch of long peices of aluminum laying on the floor!) There was no wall space that would allow a long shelf, so ... one thought led to another and pretty soon I had myself convinced I had to close up a window, put up a long shelf and ... by the way ... put in a "real" fan.

I picked a Dayton 12" fan with a shutter. Wired it up with one of those spring-wind-up swithces that turn themselves off after a while. It works great! This sucker blows! (groan ... that was bad)



Hey! A 12" fan? After a 36" box fan that didn't satisfy? Wass-up with that?

Well, the 12" fan fits beween standard wall studs, and I figured that according to it's specs it would move all the air in the shop in about 2-1/2 minutes. That's probably optimistic ... depends on no-restriction air inlet, probably doesn't count the effect of the shutter, blah, blah, blah. Anyway, if I guess half-rate, it'll clear the shop in 5 minutes, about 12 air changes per hour! Don't know what the box-fan did ... it made plenty of noise ... but it didn't move air anything like the new fan.

It gets even better when I'm squirting the paint. I use about 1/4 of my shop, with some tarps hung as "walls" to create a paint booth. The fan, you guessed it, is inside of the paint booth. Now the fan is clearing 1/4 the space, so by the numbers, it's clearing the paint booth in about a minute.

Ok, so by the numbers it ought to work. But, how's it really work? Like I already said, it works great.

Compared to the box-fan, it's like night and day. With the old box-fan setup, the paint booth would fill with a visable cloud of paint mist and after spraying and cleaning the shop would smell for at least an hour. With the new fan, there is no lingering cloud, the air remains visably clear. As I spray and clean, the odors are gone in minutes. (When done painting the paint drying on the parts continues to "exhale" fumes for a while, the fan doesn't speed that up ... I turn on the fan for an hour and leave the shop ... get a refreshment )

Disclaimer -- I'm not doing any real painting yet, just primer. I'm afraid my "temporary" paint booth may have problems if/when I want to spray real paint. I'm worried about dirt and dust ...

And a Caution -- don't even start to think that a fan is going to protect you from the bad chemicals! Use a mask, or better yet, a fresh air system to keep your lungs happy. The fan is just keeping the work space clean and clearing it out after you're done with the chemicals. It is NOT enough to keep your lungs healthy while you're spraying.

So why am I ranting on about a fan? I expected to use it when painting ... and it does that great. The bonus part is how often I use it to clear out the shop ... cleaning parts with some solvent? turn on the fan for a couple of minutes to get rid of the fumes ... slinging pro-seal? no need to suck that stink, turn on the fan ... running the saw to cut some wood? turn on the fan to get rid of some of the airborn wood dust ... sweeping the floor? turn on the fan and get rid of some of the floating dust.

If you're planning your dream shop, put in a good fan for proper ventilation.

[jim_geo]

Shortly before I set my wood working tools aside I put a recirculating air filter in the shop. It's the kind you hang from the ceiling and runs while you make dust. It works great for removing dust from the air but while shooting some lacquer I noticed it did a pretty good job of also removing the over spray from the lacquer that hangs in the air (no exahust fan). Still there was a lot of volatiles present which got me thinking that if I were to make a filter cover with activated charcoal as part of the element that might handle at least some of that problem. I'm thinking this would be most effective to use this while the paint is drying rather than actually spraying. The filter could be left running for as long as needed to help control the out gassing volatiles. Still haven't made the filter but someday I might.

[JohnR]

Okay, I am going ot dig this out of the archives again. I have been blowing air into my paint booth and have not been happy with it. I changed the fan so it sucks the air out and it seems like it will work much better.

Here is my question. My fan looks similar to the one above but is an exhaust fan from Menards. Moves quite a bit of air. My only concern is if I am going to blow myself up from paint fumes igniting!

I have no idea if this is even something I should qworry about but thought I would see if anyone has any coments.

I like fireworks, just not in my shop.

[TomNativeNewYorker]

I have seen fans in paint areas that run strictly from compressed air.

[prestwich]

Here is my question. My fan looks similar to the one above but is an exhaust fan from Menards. Moves quite a bit of air. My only concern is if I am going to blow myself up from paint fumes igniting!

If you do, can I have your tungsten bar collection?

Paint fumes are flammable, but I think you'd have to build up a pretty strong concentration of them before they'd ignite. They do make "explosion proof" motors for situations like that. Somehow they're sealed to keep the electrical sparks isolated.

Obviously, if you can't light the fumes with a match, they aren't going to light with a spark. I wouldn't paint for four hours inside a closed room and *then* turn on the fan, but if you have it going the whole time I think you're going to be OK. Remember to create a source of fresh air of equal volume to that you're exhausting.

All that being said, fumes DO ignite on occassion, with day-ruining results. One of my father's associates - who should have known better given that they were chemistry professors - hired two college students to help him clean some grimy part of his basement. They used a gallon of kerosene and a bunch of cotton rags. After an hour or so, the gas water heater touched off the fumes, and the room flashed over.

[captain_john]

Tom, that is a great idea! I have never seen one, but there should be more of them out there. I don't see a safer energy for the environment!

CJ

[LooseNut]

I put a recirculating air filter in the shop. It's the kind you hang from the ceiling and runs while you make dust. ... a filter cover with activated charcoal ...

Jim, that sounds like a nice setup . One problem with the exhaust fan that your recirculator would not have, is that within a few minutes the shop feels like the great outdoors ... in the winter it gets cold pretty fast, and in the summer it becomes hot and humid. This is more than a comfort issue if you are shooting real paint ... good looking paint requires good temps and humidity (so I've been told, so far I'm only priming ...).

Still, I like the exhaust fan getting rid of the stinky chemicals as quickly as possible. My "shop" is the garage under my house, so lingering fumes can float upstairs where they are most unwelcome.

I thought about explosions . I'm nooo expert, but my thoughts went someting like this ...

First, it's not explosive unless you have the right fuel to air ratio. Too much of either and it isn't going to ignite. Second, the exhaust fan isn't the only potential spark source.

If I take the step of explosion-proofing the fan, shouldn't I consider all spark sources? The lights? The electical switches? The electrical wiring? Static electric discharges? Even a compressed-air-powered fan has the potential problem that the fan blades can build up a static charge and spark ... like in a dusty dry environment ... hey, I'm sure the guys that designed that fan thought of that and put some sort of discharge path into the fan ... but my point is that there is a lot to worry about if you want to get rid of all potential sparks.

I think it's a much harder problem to eliminate all potential sparks than it might first appear.

So, I came to the conclusion that if I run the fan early and often (never give the vapors a chance to concentrate) I would be ok. If I can see it in the air or smell it at all, the fan is running. Now I have time to worry about other stuff .

Hey, if I'm wrong and the house blows up, I'll be sure to post here first!

[JohnR]

If you do, can I have your tungsten bar collection?

I'm shocked at your lack of concern for my RV project! If the paint booth went up it would probably ruin the wing skins as they set pretty close to it.

I went ahead and converted the booth form blowing air in to blowing air out. Well, actually Luke did it today while I was working. I haven;t shot any thin in it yet but am sure it wil be much better. As often as the fan turns the air in it I don't think I will have any problems.

Thanks for the input.