Air Scrubber Runtime Calculator
Determine how long an air scrubber (negative air machine) must run to achieve a desired number of air changes per hour (ACH) in a given space — commonly used in water damage, mold remediation, and construction projects.
Cubic feet per minute (see unit label)
IICRC S500 recommends 4 ACH minimum for water damage
Formulas Used
Room Volume (ft³):
V = Length × Width × Height
ACH Delivered by Scrubber:
ACHdelivered = (CFM × 60) ÷ V
Required Runtime (hours):
Runtime = Target ACH ÷ ACHdelivered
Units Needed to Complete in 1 Hour:
Units = ⌈Target ACH ÷ ACHdelivered⌉
Assumptions & References
- Room is assumed to be a rectangular prism with uniform ceiling height.
- The air scrubber operates at its rated CFM continuously without obstruction.
- IICRC S500 (Standard for Professional Water Damage Restoration) recommends a minimum of 4 ACH for drying environments.
- OSHA / EPA guidelines for mold remediation typically recommend 6–12 ACH for containment zones.
- CFM ratings are manufacturer-specified at the highest fan speed; real-world performance may be 10–20% lower due to filter loading and ductwork.
- Formula source: Air Changes per Hour = (CFM × 60) / Room Volume — standard HVAC/IAQ engineering formula.
- This calculator does not account for leakage, open doors, or multi-room airflow.