paint booth intake filters

Pb57

Promoted Users
Hi all,
I recently built a paint booth and have about 11000 cfm exhaust. I haven't done anything yet with the intake filter system but I don't have a lot of room for a lot of intake filters. Is there a good filter out there that allows good air flow into the booth that protects against dust decently? Would furnace filters allow more air flow through them better than the designated tacky paint booth intake filters? Im trying to control dust as best I can. The area I have now for the intake filters is 20 inches wide and 6 feet tall. Im trying to figure out what the best filters to use in this limited area. thanks Paul
 
I'm no expert on paint booth ventilation systems but 11000 cfm sounds like a high amount of air flow for only 10 sq ft of filter area. That's 1100 cfm/sq ft. I would call a filter supplier and ask them what would work. The filter type will be a trade off between air flow and how well it filters the dust. I don't see a furnace filter doing much of anything to filter dust with so much airflow. Is there anyway you can double or triple your filter area?
 
I would use sticky booth intake filters. They have an internal metal grid to help keep them from distorting. I buy them on eBay.

Don
 
These are the intake filters I use, sticky as Don suggests..


 
Thanks for the replies guys. Robert thanks for the link, I just ordered a box of 20 from McMaster and will be here tomorrow. I will put them in place and see how they work in my limited intake area with the fans full blast. it will be interesting. I will probably have to design and build a plenum for more intake area. thanks again Paul
 
Tex yes I can they are variable speed. I have filters coming tomorrow from McMaster so I will be able to tell what I need to do. thanks Paul
 
Just an update on my filter situation. I haven't gotten the filters yet from McMaster but I did make some calls to filter suppliers. No one knew how many cfm their 20 x 20 filters would pass through them efficiently. One of them was very nice and told me that the paint booth they sell has 13000 cfm exhaust and uses 20- 20x20 filters which they told me was overkill so the filters wouldn't have to be changed so often. The rep thought that using 10 or 12 of the 20x20 tacky filters should be plenty, just may have to change them more often. I looked and the 2 fans that I put in my booth are actually 10000 cfm combined. Also one of the suppliers told me that their 20x20 filters are tested at 1200 cfm but couldn't tell me what they recommended in actual use. sorry for all the useless info but thought I would pass it on. thanks Paul
 
Filters are typically rated by face velocity rather than cfm. An AFR-1 is a popular booth intake filter. They are rated for a velocity of 100 ft/min for max efficiency in stopping dust. So, if you are handling 10,000 cfm, you would divide the 10,000 cfm by the velocity of 100 ft/min and the answer is the square feet of filter area required to get that velocity. In this case, it would be 100 sq ft.

You could give up a little on the efficiency of the filter and go to twice the velocity. At that point, you'd divide 10,000 cfm by 200 ft/min and get 50 square feet of filter area. So, using 20x20 filters, your filter bank would be 3 filters tall by 6 filters wide, using a total of 18 filters. Any higher velocity and you'd risk pulling dirt thru the filters even in spite of the sticky coating. Plain old furnace filters have a max velocity rating of 300 ft/min, but they'll allow a bunch of stuff to pass thru that you don't want in your paint.

You didn't mention the size of the booth, but commercially available crossflow booths are typically designed based on a velocity thru the cross section of the booth of 100 ft/min. If, for example, your booth is 12 ft wide and 8 ft high, then the cross section is 12x8 or 96 sq ft. By the 100 ft/min rule (established by OSHA) you'd need to handle a minimum of 9600 cfm. Area in sq ft X Velocity in ft/min = cfm

If you have employees using the booth, then you have to adhere to the 100 ft/min velocity, but if you're doing your own stuff or working for yourself as self employed, then OSHA doesn't apply to you. I sectioned off one bay of my detached garage for use as a crossflow booth. Since this is just a hobby for me, I used stuff I already had. My booth is 12 ft wide and 8 ft high, so 96 sq ft. But the spray booth exhaust fan I had handles about 5000 cfm. That gives me a velocity thru the booth of just a bit over 50 ft/min. I find that's acceptable and it clears the overspray within less than 30 seconds after I quit spraying.

I suspect a lot of the regulations came about when most everyone was using conventional suction feed guns and 70% of the paint ended up in the air. I remember spraying lacquer with my old JGA years ago, and back then you did need hurricane force wind to fight the overspray. Not so much now, thank goodness :)
 
I get those mcmaster filters in a pinch. The filter lady on ebay sells a box of 20 for 95. They are also the filter I use as a prefilter in my powdercoat booth, that works like a dust collector. There are pocket filters behind that are expensive, then the prefilter in front to slow down the clogging of the pocket filters. This is a booth that does not exhaust outside. That is a part of the description for OSHA, having to have an air makeup system that introduces the same amount of air that you are exhausting to keep positive pressure in the building. So if you are not getting 10,000 cfm into the building with a huge make up system, you are going to have negative pressure anyway and suck more shop dust into those prefilters anyway.
 
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