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Calcimator

Paint Booth Airflow Calculator

Calculate required CFM, air velocity, fan sizing, and OSHA compliance for spray paint booths based on booth dimensions and type.

Inputs

%

Results

Required airflow (CFM)

12,000

Estimated fan HP

5.4

Cross-section area (sq ft)120
Air changes per hour250
Booth volume (cu ft)2,880
Duct velocity (FPM)3,820
Static pressure (in WG)1.86
Airflow DirectionCross-Draft
Duct Velocity OkYes
Meets OshaYes
How to Use This Calculator
  1. Enter Booth width (ft), Booth height (ft), and Booth length (ft).
  2. Set Booth type (1-3), Target velocity (FPM), and Filter efficiency (%).
  3. Adjust Exhaust duct diameter (in) as needed.
  4. Review Required airflow (CFM) and Estimated fan HP.
  5. Use Cross-section area (sq ft) and Air changes per hour to inform your decision.

How the result changes with Booth width (ft)

Booth width (ft)Required airflow (CFM)Estimated fan HP
1111,0005
3636,00016.2
6565,00029.3
9090,00040.5

What each input means

Booth width (ft)
Interior width of the spray booth.
Booth height (ft)
Interior height of the spray booth.
Booth length (ft)
Interior length (depth) of the spray booth.
Booth type (1-3)
1 = Cross-draft, 2 = Semi-downdraft, 3 = Full downdraft.
Target velocity (FPM)
Target air velocity. OSHA min: 100 FPM cross-draft, 50 FPM downdraft.
Filter efficiency (%)
Paint arrestor / exhaust filter efficiency.
Exhaust duct diameter (in)
Main exhaust duct diameter in inches.

What each result means

Required airflow (CFM)
Total exhaust CFM needed.
Cross-section area (sq ft)
Effective booth opening area for airflow.
Air changes per hour
How many times per hour booth air is replaced.
Booth volume (cu ft)
Interior volume of the booth.
Duct velocity (FPM)
Exhaust duct transport velocity. Must be >= 3,000 FPM.
Static pressure (in WG)
Estimated total static pressure for fan selection.
Estimated fan HP
Approximate motor horsepower for the exhaust fan.

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Booth width (ft) = 12, Booth height (ft) = 10, Booth length (ft) = 24, Booth type (1-3) = 1 = 7 input(s) provided
  2. Calculate Required airflow
    Required airflow = crossSectionSqFt * targetVelocityFpm
    12000 = 12000
  3. Calculate Estimated fan HP
    Estimated fan HP = (requiredCfm * totalStaticPressure) / (6356 * fanEfficiency)
    5.4 = 5.4
  4. Calculate Cross-section area
    Cross-section area
    120 = 120
  5. Calculate Air changes per hour
    Air changes per hour = airChangesPerMin * 60
    250 = 250

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