ACH Calculator (Air Changes per Hour) for HVAC
The ACH Calculator helps HVAC engineers, designers, and students calculate Air Changes per Hour (ACH) for a room or space. ACH is a key parameter in HVAC ventilation design to ensure indoor air quality and comfort.
ACH Calculator
ACH Formula
The standard HVAC formula used to calculate Air Changes per Hour is:
ACH = Airflow (m³/hr) ÷ Room Volume (m³)
This formula is widely used in ventilation design for residential, commercial, and industrial HVAC systems.
Example ACH Calculation
- Airflow = 1700 m³/hr
- Room volume = 340 m³
- ACH = 1700 ÷ 340 = 5.0
This means the air inside the room is completely replaced 5 times per hour.
Where ACH Is Used in HVAC Design
- Ventilation design
- Hospital and healthcare HVAC systems
- Office and commercial buildings
- Clean rooms and laboratories
- Indoor air quality assessment
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Important Notes
Recommended ACH values depend on building type, occupancy, and applicable standards such as ASHRAE and local codes. Always verify ventilation requirements during final HVAC design.
Disclaimer: This calculator is provided for educational and preliminary HVAC design purposes only. Final design responsibility remains with the HVAC engineer or consultant.
