I purchased a 12' x 20' shed to convert into a spray room for water based finishing. I've read through a lot of the previous posts which talk about building filter walls, give examples of fan sizing calculations, etc. however, there is very little discussion about the other end of the room...the air inlet side. I'd like some discussion on this topic if possible. For example,
- should the room have positive pressure or neutral/ negative pressure?
- if positive pressure, how much cfm difference between the inlet and exhaust fans?
- if negative pressure is ok, how big an inlet opening is needed for a given exhaust cfm fan? For example, if I use a 7000 cfm fan, how large does an inlet opening with filters is needed so I don't starve the exhaust fan?
- during the winter, if I bring cold fresh air into the room, how quickly do I need to be able to recover the heat when using water based products?
These are the kind of issues I need help with before I purchase some fans. Thanks
From contributor Ji
I installed a fan to push air into the booth from the outside. I sized the fan so it was just a tad over the the cfm of the booth exhaust fan. I did this by cutting a hole right by the front of the booth. Installed the fan on the outside of the hole. Built a box across the front of the booth at the top to direct the air across and into the booth. Wired it so that it comes on when I turn on the booth fan.
From contributor ji
out of curiosity , are you planning on an air make-up unit of any kind ?
From contributor Je
I plan on putting the shed next to my shop so I can tap off of my compressor and electrical. My current thought is to run duct work between the shop and the shed and bring in make up air from the shop. It is a 1000 soft shop.
I'm trying to decide if I want to have positive or negative pressure in the booth. I was thinking about putting some squirrel cage blowers in the shop to blow air into the shed. In either case I will filter the air coming into the shed/spray booth.
Does this sound reasonable?
