View Full Version : Paint exhaust fan


hig
04-26-2010, 09:53:32 AM
I really need some advice on what to use for and exhaust fan in my garage. I will be painting my Camaro in my garage that is in the basement of my house. The walls are concrete block with 2 overhead doors and 1 entry door to the outside and 1 door that goes to the rest of the basement. I'd like to go with a shuttered fan mounted in the one exterior door.

I'm thinking something like this:

http://www.grainger.com/Grainger/items/4C361?cm_mmc=Google%20Base-_-HVACR-_-Exhaust%20Fans-_-4C361

I'm concerned about it not being explosion proof, I see this motor is enclosed but not rated as explosion proof.

Can I get some suggestions? I don't want to blow myself or my house up!!!!!!!!

I see in a post that Wookie uses a large fan with a pad over it, what is everyone else using and how concerned do I need to be. I will be spraying catalized urethane products.

Thanks

BondoSpecial
04-26-2010, 10:23:13 AM
fans rated to be explosion proof are not only concerned about the motor, they also use non sparking bearings, non sparking blades.... so even a sealed motor regular fan will not really be "explosion proof". I bought a 15,000 cfm, 48" externally belt driven axial fan that I am going to use for a paint booth at some point. It won't be truly explosion proof either but it will have the motor completely out of the air stream which I figure is safer.

I doubt you are going to blow up with any fan, I have seen people using all kinds of $15 box fans with exposed motors and they figure just because they are brushless that means explosion proof (it doesn't) but I have never heard of anyone blowing up using a $15 fan either


Also, that fan is way small, 12"? I hope you were not planning on using just one of those. Usually when people use box fans they use a bunch of them, when I painted a car using box fans for exhaust I used 3 of the full size box fans under the door, and usually the plastic box fans do move a decent amount of air.

BusDriver
04-26-2010, 12:31:06 PM
Using something like the 3 fans above, there is never even close to enough fumes in the air stream at once to ignite. youd have to build up a big cloud, then turn them on to even have a chance at blowing up.

Another option is to use fans for air input (filtered of course) and let the pressure push fumes out. The fans will be blowing clean air and nothing that could ignite.

hig
04-26-2010, 01:20:14 PM
Another option is to use fans for air input (filtered of course) and let the pressure push fumes out. The fans will be blowing clean air and nothing that could ignite.

I don't think this is an option for me with the garage attached, I want to make sure I vent the fumes to the outside and try to keep them out of the house.

Cityguy
04-26-2010, 01:31:49 PM
You also need to remember to have a source of incoming fresh air as well. You need to replace the air that is being exhausted. Be careful about dust and dirt.

You do not need to extra expense of an x-proof motor. The paint fumes would need to be in a very high concentration to even have the possibility of igniting.

Also you would need something to ignite the fumes. This would require the fan motor to have a high surface temperature or some type of failure in the motor that would cause a spark. Both of these are unlikely in your case.

One last note. As far as I know there is not such thing as non-sparking bearings.

Rick

BondoSpecial
04-26-2010, 01:35:04 PM
no steel on steel is what I think would be considered non sparking. Steel roller balls on a steel shaft, in some far-out failure situation that someone could conceive, could probably spark. Bronze is non sparking. I know it sounds rediculous but the certified explosion proof fans cost a fortune and they probably had engineers sit down and go nuts designing it so they don't get sued if they sell it as explosion proof.

hig
04-26-2010, 02:17:16 PM
My garage in the basement is 26' x 32', I plan on partioning it off with plasic down the center of it so I'd end up with 26' x 16'. I'd put intake filters in the plastic wall drawing air from the unused side.

How any CFM's should I be shooting for?

If you use box fans in the bottom of the overhead door how do you seal the top of it from air coming in.

Thanks for the replies!!

BondoSpecial
04-26-2010, 02:22:17 PM
http://www.paintbooth.com/images/pdf/booth-guide.pdf

^^ Quick googling shows an exmplary cross draft paint booth listed with a 24", 8,000 cfm fan.


Another paint booth article

http://usachppm.amedd.army.mil/IH/control-of-hazards/industrial-vent/docs/Paint%20Booth%20Operations%20Design%20Review%20Checklist.pdf

^^ that article says 50 cfm per square foot of cross sectional area for a cross flow booth. So if your ceiling is 10 feet and you have a 22 foot width you would need 11,000 cfm per that recommendation.

pulpcowboy
04-26-2010, 02:23:23 PM
Is a typical screened window ok for the inflow from the outside? Would smaller bugs or gnat flies get in or is something else needed? Thanks!

BondoSpecial
04-26-2010, 02:27:37 PM
You're gonna need a lot more than that. Like very fine micron filters. Paint booth inlet filters are fibrous and also usually treated w/ sticky stuff to grab and hold even more contaminants. Also square footage of filter media has to be considered because if you pull too many cfms through a small filter the velocity is going to be high enough that the dirt will pull through the filter and render it pretty useless. Which is why you see booths have not only high air flow but also lots and lots of filter surface area. Don't try to pull 8k cfms through a 20"X20" single filter, not gonna work

Guys will use furnace filters for home built stuff which are fiberglass but a real paint booth fiberglass inlet filter is going to be much thicker and denser (and treated most likely)

79camaro2001
04-26-2010, 02:28:40 PM
depends on your outdoor environment. if it's dusty then the screen won't do any good.

Check out the local hardware store for air filters. you can get some cheap ones at different size and you can place them over your incoming air to reduce dust.

Same for your exhaust fans to reduce the paint fume painting your house as it exit the garage.

79camaro2001
04-26-2010, 02:33:39 PM
Guys will use furnace filters for home built stuff which are fiberglass but a real paint booth fiberglass inlet filter is going to be much thicker and denser (and treated most likely)

True, but those are designed for repetitive uses and so on. We are talking about a one day paint job that isn't as critical as a car being painted professionally. As long as he has enough surface area for the air to pull though basic home filter would be better then a open box fan with no filters on it.

Painting in a non paint booth setup, I would be more concern with sealing all openings and also cut down on the big partials. Fine dust wouldn't bother me too much as that can be cut and buff out pretty easy.

earlysecond
04-26-2010, 05:23:40 PM
Steve,

I have a one bay garage that with a 10 ft. wide standard garage door. I built a block off out of 2X4 lumber and attached celotec insulation to fill the rest of the air space. My 20" 1/2 hp motor fan mounts in the block off. I seal the top of the outside of the garage door with stapled plastic sheeting and duct tape.

The inlet is a bank of filters on the back "wall". The back wall is a partition fashioned out of lumber designed to hold a full 10 foot row of filters at the top, it as a door as well, Ace hardware sells adhesive zippers for this purpose.

I have painted half of the total overalls that I have done [5] in this booth and nowhere else. Days before I paint I strip the old plastic sheeting off of the walls hose and scrub the floor and blow out the dust from every nook and cranny WHILE the booth is set up with the fan running the final couple of times. I often let the booth with the clean car sit in there for days and blow it off occasionally.

You can ground the car to the floor with a piece of chain, I am not sure that helps. Much of the dust will come either off the car or off of the painter. Keeping the "booth" wet WHILE you spray is generally considered to be a bad idea. . .I will skip the explanation but tell you that once when I tried this it was an epic failure.

You do NOT want to build a wind tunnel. Rather you need to be able to spray down the side of a car with clear on a gun that is properly diailed in and still be able to see the whole time you are painting.

Of course you want a respirator or supplied air system. Shower immediately after spraying.

A lot of what makes a home booth work or not is sufficeint exhaust, clean filtered incoming air. Enough room to work around the car without hitting walls or the car. . .AND. . .wait for it. . . LIGHTING. I am not sure that you can have too much. The lights are still pretty cheap. I leave most of mine up all the time as I like it bright in my garage.

If you have a part or two that need painted off of the car. Set everything up and try them first.

You have gotten good advice before I chimed in and hopefully you will get even better ideas. This is what I do and most of the time it works pretty well.

Good Luck,
Brent

hig
04-28-2010, 05:54:32 AM
Thanks for everyone's replies, I'll be looking for some exhaust fans.