Paints & Coatings Resource Center

Ask the Expert Question-and-Answer Archive

by Ron Joseph

October, 2005

Changing Filters in Spray Room Based on Pressure Differential

Q. We just installed a paint booth at our facility. There is a pressure gauge installed across the filters. Is there a relationship between the air velocity and the pressure in could use to determine when the filters needed to be cleaned

A. The manometer on the side of a paint spray room measures the pressure differential across the exhaust filters. Regardless how plugged the filters are with overspray, the faster the air flow the higher the differential. OSHA recommends that we have an air velocity of 100 fpm in most spray rooms. To determine when you should change your filters I suggest that you measure the differential when the filters are new and when the velocity is >100 fpm. Then monitor the differential over time while the filters load up with overspray. Frequently measure the air velocity through the spray room. When the velocity falls below 100 fpm, record the pressure differential and use this value as your baseline for changing the filters.

If you would like to learn much more on spray booths, air velocities, filters, spray guns, etc., please visit


Ron Joseph

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