56 



KGGS IN COLD STORAGE. 



Plenum vs. 

 vacuum 

 method of 

 ventilation. 



Advantages of 

 the plenum 

 or pressure 

 method. 



controllable to suit the demands of those who are 

 ventilating-." 



There are two general methods, with some modifi- 

 cations, for handling- air for ventilation: The plenum 

 or pressure method, in which the fresh air is forced 

 into the room ; and the vacuum or exhaust method, in 

 which the foul air is drawn out. The exhaust method 

 is to be avoided for ventilating- cold storag-e rooms, 

 for reasons which we shall see presently. With this 

 method, sometimes the exhaust steam from an engine 

 is utilized to induce a draft of air upward from storag-e 

 room, by heating- the air in a stack or ventilation flue 

 connected at its lower end with the room to be ven- 

 tilated. In some cases no provision is made for an in- 

 flow of fresh air, in which case it will seep in at every 

 crack, crevice and pore (by reason of the partial 

 vacuum created by exhausting- the foul air out), bring- 

 ing- a load of moisture and g-erms of disintegration 

 into the storag-e room. This exhaust steam method 

 is no different in its result than if a fan were placed 

 so as to draw the air out of the storag-e room under 

 conditions which are otherwise the same as described 

 in connection with the exhaust steam method. Should 

 we provide an inlet for fresh air, throug-h proper ab- 

 sorbents, the same law would be operative, only to a 

 lesser degree, as a partial vacuum must, in any case, 

 be created before the air from outside would flow into 

 the room, tending- to the dang-erous air leakag-e already 

 fully discussed. 



The plenum or pressure method is by far the best 

 for our purpose. The air should be forced into the 

 room by a fan, after first properly cooling-, drying 

 and purifying- it. An outlet for the escape of the foul 

 gases which it is desired to be rid of, should be pro- 

 vided near the floor, as these gases, by reason of 

 their greater gravity, tend to accumulate in the lower 

 part of the room. It will be observed that forcing 

 the fresh air in creates a pressure inside the room, 



