Rooms in which water closets are situated should be well ventilated to insure a frequent change of air. This requirement is absolute in large toilet rooms containing many washout or other non-deodorizing closets.

A method of ventilating closet compartments is shown in Fig. 150. The separate flues in this system should never be less than 6 inches in diameter, and when possible to place a small steam or hot water coil in the bottom of each flue, the direction of the current of air is made positive. Ventilation flues from different compartments should extend separately through the roof; when joined to flues from other rooms they serve as sound conductors from one room to another.

Fig. 150

Local vents from closets should not be used in lieu of ventilating the compartment. A local vent is a small pipe of from 1 1/2 to 2 inches in diameter that is connected to the bowl of a closet and extends through the roof. They are so unsatisfactory that in practice they are seldom used.