Air Changes per Hour Calculator: worked example
This example is generated from PROFENG's own default input set and the implemented relationship. It is not copied from a cited publication.
Relationship
ACH = V̇×3600 / room volume
This calculator determines air changes per hour from airflow, room volume. Use it for HVAC and building-services screening with transparent air, thermal or flow assumptions.
Inputs
- Airflow (flow) = 0.5 m³/s
- Room volume (volume) = 300 m³
Working
(0.5)*3600/(300) = 6 ACH
Air changes per hour: 6 ACH
Assumptions and limits
- Air or fluid properties are represented by the entered values.
- The calculation represents steady operation unless the formula explicitly includes time.
- Room, duct or envelope geometry is idealized by the displayed relationship.
- Airflow is treated as a steady volumetric rate.
- Room volume is the effective air volume for the intended ventilation calculation.
- ACH is a ventilation-rate descriptor, not by itself an indoor-air-quality compliance determination.
Formula source and acknowledgement
ASHRAE, ASHRAE Handbook—Fundamentals, 2025 volume, 2025, ASHRAE. Credit belongs to the cited author(s)/publisher; PROFENG presents its own implementation and does not imply endorsement.
Automated verification passed – 30 September 2026 – six numerical cases checked, with dimensional checks and an independent implementation where applicable.
This worked example is for engineering screening and education. Replace defaults with traceable project data and confirm the method, assumptions, standards and equipment information before design, procurement or operation.