Air Changes per Hour (ACH)

Convert between ACH, CFM, and room volume — with code reference ranges
Solve For
ACH
air changes/hr
Minutes per Change
min / change
Code Requirement
ACH Reference — Selected Space Types (IMC / ASHRAE 62.1)
Space TypeMin ACHSource
Office4–6ASHRAE 62.1
Conference Room6–10ASHRAE 62.1
Classroom6–8ASHRAE 62.1
Exam Room (Medical)6 minASHRAE 170
Patient Room6 min (2 OA)ASHRAE 170
Operating Room20 min (4 OA)ASHRAE 170
Laboratory6–10 (fume)ASHRAE 62.1
Commercial Kitchen15–60IMC Table 403.3
Restroom (public)2 CFM/SF or 50 CFM/fixtureIMC 403.3
Parking Garage0.75 CFM/SFIMC 404
Free 14-Day Trial  ·  No Credit Card

Do the full calculation in AIM Works

This calculator handles one step. AIM Works runs the complete MEP design workflow — thermal load calculations, duct & pipe networks, equipment selection, code compliance, and an AI design assistant — in one tool.

  • ✓  ASHRAE 62.1 ventilation + CLTD/CLF/RTS load methods
  • ✓  Darcy-Weisbach pipe & duct network solvers
  • ✓  ASHRAE 90.1 / IMC / NFPA compliance checks
  • ✓  20 free AI design messages included in trial
Try It Free for 14 Days →
No credit card  ·  Cancel anytime
See plans & pricing →