86 VETEEINAEY HYGIENE 



late whether under ordinary conditions of wind-velocity 

 they will admit sufficient air for the whole of the occupants. 

 The doors had better be omitted from this calculation. 



To determine the proper distribution and mixing of air, 

 and also as a guide to the inlets and outlets, generate some 

 smoke by burning a little damped straw, and observe the 

 points noted ; do the same with doors and windows closed, 

 and observe the inlets and outlets under these conditions. 



The velocity of the incoming air may be accurately 

 measured by means of an anemometer, an instrument with 

 sails which revolve by the wind, the number of linear feet 

 of air which pass in a given time being recorded on a dial. 

 The number of linear feet multiplied by the section area of 

 the opening gives the cubic discharge. 



In default of an anemometer, the Beaufort scale of wind, 

 (p. 80) must be employed. 



The examination of the air by the senses must be made 

 immediately the stable is entered, and the impression at 

 once recorded. The observer should take the greatest care 

 to have been in the open air some httle time before making 

 the observation. 



This test enables the amount of respiratory impurity to 

 be ascertained with a considerable degree of accuracy, 

 provided the atmosphere is not too impure. 



The Amount of CO2 per 

 1,000 Vols, of Air duo to 

 . „ „ , Kespiratory Impurity is 



VViien the air smells fresh, or not differing 



sensibly from the outside air... ... =-2000 



When the air smells rather close ... =-4132 



When close ... ... ... ... = -6708 



When very close ... ... ... = -9054 



If the amount of respiratory impurity has been estimated 

 as above, it is possible to determine by de Chaumont's 

 equation the amount of fresh air which has been supplied. 



- = cl where e = the amount of CO, exhaled per hour in 

 cubic feet, viz., 3. 



Fi = the observed ratio of vitiation per 1,000 

 volumes. 



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