DAIRY INSPECTION 133 



part of the stable, but also from the lower. Inlets are placed 

 in all of the outer walls of the stable if possible, with the inside 

 opening just under the ceiling and the outside opening five feet 

 lower (Fig. 9). 



The number and size of inlets necessary will vary with 

 weather conditions, and it is therefore desirable to have as 

 many as possible and then use as many as may be needed. 

 Weather conditions exert considerable influence on the air in 

 stables ventilated by any system which depends for its opera- 

 tion on natural forces. When the atmosphere is still or moist, 

 the ventilation is often inefficient in stables which under other 

 conditions are well ventilated. 



A cow requires 59 cubic feet of air per minute and it is 

 estimated that air will pass through a flue at the rate of 290 

 to 300 feet per minute. The minimum number and size of 

 inlets and of outlets required may therefore be calculated accord- 

 ing to the following formula : * 



No. cows in stable x 59 x J44 gq in = Total cross-sectional area in square inches 

 300 of inlets and of outlets. 



By dividing the total cross-sectional area by the number of 

 inlets and of outlets, the cross-sectional area of each inlet and 

 outlet is ascertained. The number of inlets and of outlets will 

 depend upon the size of the stable. Inlets should not be over 

 12 feet apart ; closer if possible. Several outlet flues of moder- 

 ate size in different parts of the stable are preferable to one 

 or two large outlets. 



Each inlet should be provided with a sliding door or other 

 contrivance by which it can be conveniently opened or closed. 

 The outlet flues should extend from the floor to 6 feet above 

 the highest point of the roof and should be capped with a hood 

 1 foot above the top. If they cannot be placed where they will 

 not act as obstructions, they may be hinged at the ceiling so that 

 they can be drawn up out of the way temporarily (Fig. 10). 

 Each outlet flue should have two openings into the stable, one 

 just under the ceiling and the other a foot above the floor, both 

 openings being provided with doors which can be readily opened 



1 Wisconsin Exp. Sta., Bull. No. 266. 



