Occupancy limits are set as per floor space area rather than ACH. Generally, you would want to give ~5 square meters of unencumbered floor space per person to establish occupancy limits. The BC Building Code dictates the determination of occupancy limits. See this link: https://www2.gov.bc.ca/gov/content/safety/emergency-preparedness-response-recovery/fire-safety/legislation-regulations-codes/occupant-load. As specified in the Industrial Ventilation — A Manual of Recommended Practice, “Air changes per hour” or “air changes per minute” is a poor basis for ventilation criteria where environmental control of hazards, heat, and/or odors is required. Air changes per hour are calculated by taking the supply airflow into the room (in units of cubic feet/min) times 60, and divided by the volume of the room. Occupancy limits are set accordingly with the area of the room, as well as intended use of the room. See attached PDF for this formula to determine relationship between ACH and Occupancy limit. From the numbers that provided, further information is needed for the calculation (Area of the room and acceptable area/person).