How is Fresh Air Changes per Hour defined?

Fresh Air Changes per Hour (ACH) is defined as the number of times the air within a given space is replaced with fresh outdoor air in one hour. This measurement is crucial in determining the effectiveness of ventilation systems in providing adequate fresh air to occupants and ensuring indoor air quality.

When calculating ACH, an understanding of the space's volume and the airflow rates is necessary. The metric helps assess how well a space is ventilated, which directly impacts the health and comfort of the occupants. Regular changes of stale indoor air for cleaner outdoor air can help mitigate the buildup of pollutants, odors, and humidity levels.

In contrast, the total air volume supplied by HVAC systems, efficiency ratings of ventilation units, and the volume of stale air exhausted do not describe the specific measure of how often the air in a space is being replaced with fresh air. While these factors are related to ventilation and air quality, they do not capture the core concept of Fresh Air Changes per Hour.