Air change is more impoant for ventilation than the cubic space requirement. It is recommended that in the living rooms, there should be 2 or 3 air changes in one hour; in work rooms and assemblies 4 to 6 air changes. If the air is changed more frequently, i.e., more than 6 times in one hour, it is likely to produce a drought which should be avoided. The number of air changes per hour is calculated by dividing the total hourly air supply to the room by the cubic capacity of the room. Ref: Textbook of Preventive and Social Medicine by K Park, 19th edition, Page 595-596.