88 VETERINARY HYGIENE 



The modern view is to regard animal houses as necessary evils. 

 If they cannot be dispensed with altogether, the only alternative is 

 to make them as little " house-like " as possible, and to keep in mind 

 that what is required is protection from rain, driving wind, excessive 

 cold and damp and to provide facility for feeding and attendance. 



THE AMOUNT OF AIR REQUIRED. Ventilation has been described 

 as " essentially a question of removing the curtain of heat which 

 surrounds the body." It is no longer looked upon as a chemical 

 or pulmonary problem, but as one which is physical and cutaneous. 

 It is known that the mere fact of causing the hot foul air to 

 circulate, as by electric fans, is sufficient to give at least a temporary 

 relief (Hill), but for the improvement to be lasting the foul air 

 must be replaced by pure air. 



Since we know within a reasonable range of error the amount 

 of CO 2 excreted hourly by the various domestic animals and have 

 determined what may be regarded as a permissible addition to the 

 air in a building, a very simple formula will show how much fresh 

 air must be admitted every hour that there may be no accumulation 

 of impurity. 



De Chaumont's formula for calculating the amount of fresh 

 air required is as follows : 



e 



-x ioo = a 



P 



where e is the amount in cubic feet of CO 2 excreted per hour, 

 p is the percentage of permissible CO 2 impurity and d is the 

 amount in cubic feet of fresh air required per hour. 



It has been stated on a former page that if the air contains no 

 more than 0-02 per cent, of CO 2 above the normal (0-03 per cent.) 

 that a very satisfactory condition exists, but that 0-06 per cent., or 

 a total of 0-09 per cent., may be allowed, although the latter should 

 be regarded as the limit of impurity. The high standard should be 

 the aim of all hygienists, but it is often necessary to effect a com- 

 promise between the two. 



The formula to calculate the amount of fresh air required hourly 

 by an average man will read : 



0.6 



X 1 00= 3000 cubic feet of air per hour ; 



0.02 



since a man discharges 0-6 cubic foot of CO 2 per hour. 



A horse of the cab or vanner type or a medium weight rider 

 discharging approximately 3 cubic feet of CO 2 per hour will, under 

 the high standard, require 15,000 cubic feet of air per hour, or, 



