Why You Can't Recirculate Spray Booth Air

Filtering and re-using spray room air is not feasible, as this thread explains. October 27, 2005

I want to build a new spray booth and I want to recycle the air (pulling it through the exhaust, cleaning it and putting it back in) for easier heating in the winter, and drier air in the summer. What kind of system do you use, and what kind of filters?

Forum Responses
(Finishing Forum)
From contributor A:
Everyone would do this if it was possible. You need to replace the air. You can't filter the volume of waste from your air safely. Even large operations with the resources to do this replace with tempered air. Look into air make-up equipment.

From contributor B:
You would need to have a massive box of activated charcoal, the same stuff they use in your respirator filters. I'm sure this would eat up a good portion of your budget, and I donít know how you would get rid of the stuff after it was saturated.

From contributor C:
It's not plausible to recirculate the air back into the sprayroom. Filter banks trap the solids content of your over spray and the gaseous solvents are then exhausted out. Trying to re-circulate the air would only filter out the solids and would cause a dangerous level of gaseous solvents. If you didn't blow up your finishers in an explosion, you'd kill them from oxygen deprivation as the increasing level of solvents rapidly displaces the oxygen in the roomís atmosphere.

A giant filter cartridge would be cost prohibitive compared to heating and still wouldn't deal with the decrease in oxygen that the finishers are breathing. The only way a finisher could survive in such an atmosphere is by using a supplied air respirator or a self contained breathing apparatus. Even then, the explosive atmosphere isn't worth the risk of killing your finishing crew and burning down your business, for the sake of trimming your heating bill. If you're building a spraybooth or room from scratch, look into radiant floor heating with the piping laid beneath the floor. Or check into other heating methods, but don't screw with the fresh air make up system. Vent the nasty stuff where it belongs, away from your finishing crew. This subject always bothers me. Why is it that all cost-cutting measures are looked at in the finishing room first?

From contributor A:
Why wouldn't you screw with the fresh air make-up system? It seems easier than jack hammering the floor for radiant heat, which will disappear as soon as the booth is kicked on. Tempered air make up is the industry choice.

From contributor C:
To contributor A: The underfloor heating suggestion was if he is starting from scratch, with no existing floor to jackhammer through. As for a tempered system, thatís not what he's looking to do. He's looking to re-circulate the already heated, contaminated and oxygen depleted air from the spraybooth. A tempered system doesn't screw with fresh air - it's just another method of heating fresh air.