82 VETERINARY HYGIENE 



Mackenzie and Russel* investigated the condition of the air 

 in two poultry houses of different types and found that there was 

 present 0-067 and 0-082 per cent, of CO 2 , and that the birds 

 remained healthy in both houses. They therefore assume that the 

 air of poultry houses may contain with safety from 0-07 to 0-08 

 per cent, of CO 2 , and consider that 0-09 per cent, should be the 

 maximum amount that should be allowed. Reiset and Regnault's 

 experiments showed that poultry take up about 0-03 cubic foot 

 of oxygen per hour and give out about the same quantity of CO 2 . 

 Richet's trials at a later date, 1890, gave approximately the same 

 results. 



Owing to the great importance of the maintenance of the health 

 of workers in factories and of children in schoolrooms, hygienists 

 have studied closely the air conditions in factories and dwellings 

 and, inter alia, have determined what they consider to be the 

 maximum amount of CO 2 that should be permitted. By the Cotton 

 Cloth Factories (Amendment) Act, 1887, the amount of CO 2 in 

 these factories is not allowed to be greater than 0-09 per cent, 

 of the atmosphere. Later, in 1902, Haldane and Osborne recom- 

 mended that the maximum should be 0-12 per cent, during the day 

 or when artificial illumination was by electricity, and that 0-20 

 per cent, should not be exceeded at night when the illuminant was 

 gas or oil. 



It does not appear to be practicable in the case of schools and 

 workshops to keep the air as pure as theoretically would seem 

 advisable. 



It is obviously impossible, however good any system of ventila- 

 tion may be, to maintain the air in a building of the same composi- 

 tion either chemically or physically as pure outside air, therefore a 

 certain amount of general impurity is conceded as permissible. 

 The limit of this impurity is indicated when the air is found to 

 contain an additional 0-02 per cent, of carbon dioxide to that 

 present in pure air, viz., 0-03 per cent. Theoretically, then, the 

 air in any building housing either animals or men should not contain 

 more than 0-05 per cent, of CO 2 , which quantity is composed 

 of two fractions, 0-03 per cent, normally present (and therefore 

 not an "impurity" as it is frequently called) and 0-02 per cent, 

 a permissible impurity. 



With the veterinary hygienist rests the responsibility of deciding 



what degree of pollution should be permitted in animal buildings. 



If an unnecessarily high standard be set it is not likely to be accepted 



by those financially interested ; on the other hand, if the standard 



* Trans. High, and Agric. Soc., 1908. 



