AIR AND VENTILATION 81 



feet, a sheep, 1 cubic foot, and a dog of about 50 Ibs. 0-3 cubic 

 foot. 



The amount of carbon dioxide in a building is increased by the 

 ombustion of coal-gas and oil for illuminating purposes. An 

 ordinary gas jet produces about 3 cubic feet of CO 2 per hour, and 

 in addition some water vapour. An incandescent burner con- 

 sumes relatively less gas and therefore produces correspondingly 

 less heat and fewer impurities. Oil lamps such as are used in byres 

 and stables add to the air combustion products approximately 

 equal to those of an ordinary gas burner. 



The Significance of Carbon Dioxide. The air of inhabited 

 places always contains an amount of carbon dioxide greater than 

 that found in pure outside air. Experimental evidence is to the 

 effect that no harm results to man until it accumulates to about 

 1 per cent, of the atmosphere, or nearly 40 times the quantity found 

 in normal air. 



Though this amount may be found occasionally in very foul 

 rooms, it is exceptional for it to be present in greater quantity 

 than 04 per cent. Baskerville found the general average in 

 American schoolrooms to be 0-09 per cent. 



Some interesting and valuable data concerning the percentage 

 of carbon dioxide found in cow byres are supplied from the experi- 

 ments initiated by the late John Spier and carried on by Dr. Douglas 

 and Professor Hendrick* for the purpose of determining the degree 

 of pollution of the air in commercial byres, and, at the same time, 

 to study the influence of temperature on milk yield. It is certain 

 that the byres used were above the average commercial standard 

 both as regards construction and cleanliness. The average CO 3 

 content of sixteen byres was recorded as 0-248 per cent., and for two 

 exceptionally well-ventilated buildings the average was found to 

 be 0-11 per cent. The minimum amount found in what may be 

 regarded as a " model " byre was 0-05 per cent., and the maximum 

 in the same byre 0-17 per cent. These experiments were con- 

 ducted during the winter months from December to March, that is 

 during the period when it is most difficult to keep byres sufficiently 

 well ventilated and at the same time warm. The CO 2 was found 

 in greatest amount in the evening a short time after the byres were 

 closed for the night. Hendrick attributes this to the fact that the 

 digestive system of cows is working harder during the evening 

 a short time after feeding than in the early morning when they have 

 been resting, and we know that gaseous exchange varies with intens- 

 ity of metabolism. 



* Trans. High, and Agric. Soc., 1909, 1911, 1913. 

 6 



