Re: Paint Booth

Nelson Moyer

One thing that hasn’t been mentioned is make-up air, i.e. air supply to replace the air you’re blowing out through the booth. If you’re drawing a negative pressure in the room, you’re reducing the efficiency of the fan’s rating, and you’re not blowing as much air as you might think, especially if you have a tight house. Cracking a window will provide make-up air. That comes from experience during a career in microbiology laboratories using biological safety cabinets from Class 1 to Class 3. HVAC systems in negative pressure labs are designed and balanced to function with and without BSCs operating, but your house doesn’t have those engineering controls.


Nelson Moyer




From: [] On Behalf Of Matt Goodman via
Sent: Thursday, June 04, 2020 1:50 PM
Subject: Re: [RealSTMFC] Paint Booth


Nelson raises a point worth considering - how much air is moved.


I have a off the shelf Paasche booth that vents inside the basement. That was fine for short paint sessions, or slightly longer sessions wearing a respirator - neither of which is a good long term solution.


About two years ago, I started researching how much air (in cfm) I’d have to move given the distance and number of turns the exhaust would have to navigate.  I found the following site very useful for those calculations:



I also described my use case and calculations from the above site in a post on the MRH forum, and got some decent help (from one guy in particular). In the research process, I also found a HVAC guy who has air booth plans that is well done (Jim Hayes, you may especially find it useful). All that is in the post here:



This whole CFM topic turned out to be more of a brain-squeezer than I expected!


Matt Goodman

Columbus, Ohio US

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