AIR AND VENTILATION 89 



\\ here the limit of impurity is allowed, 5000 cubic feet per hour as 

 is here shown : 



High standard : . x 100= 15,000 cubic feet. 



0.02 



Low standard : . . ^ x 100 = 5,000 cubic feet. 



o.oo 



If the quantity of carbon dioxide in the air is determined by 

 analysis, it is possible by the use of this formula to calculate the 

 amount of fresh air that has actually been supplied each hour. 

 Suppose, for instance, that the air in a cow byre is found to contain 

 0-20 per cent, of CO 2 . Find the amount of fresh air admitted 

 per hour, the cows being large animals on a full productive diet. 



e 



- x \oo = d 



p 



where e = the amount of CO 2 discharged per hour ; p' = the per- 

 centage of CO 2 found in the air less that normally present; and 

 d f = the amount of air in cubic feet that has been supplied. 



rX 100=3530 cubic feet of air. 



(0.20 0.03) 



On page 90 will be found a table giving the amount of air 

 required hourly by the various domestic animals both for the high 

 and low standard. 



CUBIC SPACE. Necessary as it is to know how much fresh air 

 must be supplied during a given time, it is equally important to 

 appreciate how many times cows, horses, pigs, calves and other 

 domestic animals can stand the air in their quarters being changed 

 during the period. 



According to the power of each to withstand frequent air change, 

 that is their degree of susceptibility to draughts, will depend the 

 amount of air-space to be allotted to each animal in a building. 

 It is of the greatest importance to realise that each, let us say cab 

 horse, must have 15,000 cubic feet of fresh air every hour if a high 

 standard of purity is to be maintained, irrespective of the size of 

 the stable. Supposing the cab horse to be confined in a small loose- 

 box having a total capacity of 600 cubic feet, if 15,000 cubic feet 

 of air is made to pass in and 15,000 feet made to pass out each hour, 

 the entire air in the box would be changed 25 times each hour, 

 or once in every 2\ minutes, a condition under which it would be 

 unreasonable to expect any animal to live. 



If, on the other hand, the horse be stabled in a box having a 

 capacity of 2000 cubic feet, though the same amount of air would 



