How much fresh air in HVAC?

The amount of fresh air required in an HVAC system depends on the size of the space, the number of occupants, and the type of activities taking place. Generally, the minimum amount of fresh air required is 15 cubic feet per minute (CFM) per person. However, for spaces with higher occupancy or more strenuous activities, the amount of fresh air should be increased to 20 CFM per person. Additionally, the fresh air should be balanced with the return air to ensure proper air circulation and temperature control.