The volume of air required is determined by the size of the space to be ventilated and the number of times per hour that the air in the space is to be changed. Table 3-4 shows the recommended rate of air change for various types of spaces.
In many cases, existing local regulations or codes will govern the ventilating requirements. Some of these codes are based on a specified amount of air per person and on the air required per square foot of floor area. Table 3-4 should serve as a guide to average conditions. Where local codes or regulations are involved, they should be taken into consideration. If the number of persons occupying the space is larger than would be normal for such a space, the air should be changed more often than shown.