How is ACH calculated, and what are the units of measurement?

Air changes per hour (ACH) is calculated using the formula: ACH = (cfm / 60) / Vol, where cfm is the quantity of airflow in cubic feet per minute, and Vol is the volume of the conditioned space in cubic feet. The unit of measurement for ACH is air changes per hour, which represents the number of times the air in the space is replaced in one hour.