SYSTEMS OF VENTILATION 333 



366. Heating and Ventilating the Several-room School 

 Building. Forced systems of ventilation are generally used in 

 modern school buildings containing several rooms. As was 

 the case in the one-roomed school, so here we find that the 

 heating and ventilating systems are usually combined. When 

 such large quantities of air must be moved the gravity system 

 is not adequate, the forced system must be employed. More- 

 over, school buildings containing several rooms are likely to 



FIG. 236. Stove with jacket cut away. 



be heated by steam and steam power is therefore available for 

 driving the FAN, or BLOWER, if desired. 



Forced systems of heating and ventilation may be of the 

 propulsion type, known as the PLENUM SYSTEM, or it may be 

 the SUCTION SYSTEM, or a combination of the two systems. 



367. The Plenum System. In the PLENUM SYSTEM the 

 blower or fan is usually placed in the basement and forces all the 

 fresh, heated air needed for heating and ventilation through 

 air ducts into the various rooms. The air in all the rooms is, 



