How do I calculate paint booth airflow?

Open face area × target velocity gives the exhaust requirement. Divide by fan and filter efficiency for the fan rating: a 96 ft² face at 100 ft/min needs 9,600 CFM and a 10,667 CFM fan at 90% efficiency.

What face velocity does a paint booth need?

The common design figure for open-face liquid booths is 100 ft/min average across the opening, with OSHA 1910.94 and the booth listing setting the binding value. Your inspector's number wins.

Why divide by fan efficiency instead of multiplying?

Because losses come out of the rating before air reaches the face. A 9,600 CFM fan passing 90% delivers 8,640 at the face; dividing sizes the fan so the face actually gets its 9,600.

What is the dirty-filter reserve for?

Exhaust filters blind as they load, and flow falls until changeout. The reserve, 10 to 25% by practice, keeps face velocity legal the day before the filters are swapped rather than only on installation day.

Finishing calculator

Paint Booth Airflow Calculator

Size a liquid booth's exhaust and the fan rating behind it. Enter the open face area, target face velocity, clean-filter efficiency and dirty-filter reserve.

What this calculator does

Exhaust and fan rating for a liquid spray booth from face area, design velocity, system efficiency and filter reserve.

Formula used

Exhaust at face = booth opening face area × target face velocity
Rated airflow required = exhaust at face ÷ fan and filter efficiency
Efficiency allowance = rated airflow − exhaust at face
Fan rating with dirty-filter reserve = rated airflow × (1 + reserve)

Inputs explained

Booth Opening Face Area: Open cross-section air crosses: opening width × height, slots included.
Target Face Velocity: Design velocity across the opening; 100 ft/min for open-face booths.
Fan and Filter Efficiency: Share of rated fan flow that survives clean filters and duct.
Dirty-Filter Reserve: Extra rating so face velocity holds as filters load toward changeout.

How to use the result

Best suited to specifying the exhaust fan for a new booth, checking fan duty through a filter cycle, diagnosing a failed smoke test.
Capture arithmetic, not a compliance ruling; NFPA 33 and your inspector govern. Turbulence and part blockage move real capture beyond face-average velocity. Makeup-air heating is priced on the booth operating cost page, not here.

Current U.S. benchmarks

Industrial electricity averages 9.77 cents per kWh across the U.S. (EIA, Jul 2026), up 4.7% from a year earlier. Energy-intensive steps carry this directly into unit cost.
The producer price index for industrial chemicals stands at 336.006 (BLS, Aug 2026), up 13.3% from a year earlier. Quotes priced off last quarter's material cost miss this move.
The U.S. has 14,543 chemical manufacturing establishments employing about 911,245 workers (Census County Business Patterns, 2023).

Common questions

How do I calculate paint booth airflow? Open face area × target velocity gives the exhaust requirement. Divide by fan and filter efficiency for the fan rating: a 96 ft² face at 100 ft/min needs 9,600 CFM and a 10,667 CFM fan at 90% efficiency.
What face velocity does a paint booth need? The common design figure for open-face liquid booths is 100 ft/min average across the opening, with OSHA 1910.94 and the booth listing setting the binding value. Your inspector's number wins.
Why divide by fan efficiency instead of multiplying? Because losses come out of the rating before air reaches the face. A 9,600 CFM fan passing 90% delivers 8,640 at the face; dividing sizes the fan so the face actually gets its 9,600.
What is the dirty-filter reserve for? Exhaust filters blind as they load, and flow falls until changeout. The reserve, 10 to 25% by practice, keeps face velocity legal the day before the filters are swapped rather than only on installation day.

Related guides

Running Paint Booth Airflow as a Daily Operating System

Last reviewed 2026-10-01.