Ask the Expert Question-and-Answer Archive

by Ron Joseph

August, 2001

Disruption of Airflow in Spray Booths

Q.If I have 8 air handlers providing 492,800 CFM of airflow, and 8 exhaust fans removing 492,800 cfm of air and one of my air handlers goes down, will airflow across the booth remain the same?

A. I presume your eight air handlers provide a total of 492,000 cfm? Can we assume that you are not saying that each of the eight air handlers provides 492,000 cfm?

Regardless of what the number is, yes, if one of the air handlers goes down you can expect the air flow to change. When you refer to "airflow" this can mean cfm, velocity (fpm), and turbulence.

If one of the air handlers goes down, I would expect the total cfm to go down, especially if the other seven are not equipped with variable frequency drives (VFD), and to the best of my knowledge your system is not, (or was not) equipped with VFD's. If the cfm drops, so will the velocity in fpm. It is entirely possible that there will be dead spots in which there is no airflow at all. Depending on the initial air velocity it is possible that the the adjusted velocity will fall below 100 fpm. Worse, you can expect more turbulence inside the booth since the direction of the airflow will change. In some painting facilities I have seen overspray move from the tail of an aircraft (which is close to the exhaust filters of the booth) settle on the nose of the aircraft, which is furthest from the filters. As you know, this can cause havoc with the paint crew who must then do extensive rework on contaminated areas.

I hope this helps, but if I have misunderstood your question please give me more details so that I can be more helpful.