Some Aspects of Town Air. n 



Some Aspects of Town Air as contrasted with that of 

 the Country. By G. H. Bailey, D.Sc, Ph.D. 



(Received October jrst, iSgj.) 



The constituents of the air which are usually determined 

 are the oxygen and the carbonic acid. The variations in 

 the oxygen are small, and for the most part fall between 

 21 per cent by volume as a maximum and 20*9 as a 

 minimum, though in special cases lower values (e.g. Angus 

 Smith's determination of 20*26 in mines) have been recorded. 

 The minimum for carbonic acid gas in country air may be 

 taken at '029 per cent rising in cloudy weather and at night 

 time to '033, though it frequently approaches '04. For town 

 air -04 may be taken as a favourable record, while in foggy 

 weather -oy is the maximum (Angus Smith). It is thus 

 seen that the variations in the amount of oxygen and of 

 carbonic acid are comparatively small, and in the case of 

 the latter even the record for highly polluted air is only 

 about double that usually found in country air. Carbonic 

 acid in the air of dwellings and public buildings increases to 

 as much as tenfold its normal value, and in such cases a 

 mere determination of this constituent of air is a 

 sufficient indication of the nature of the air. Excepting 

 the case of dwellings, carbonic acid gas dees not afford 

 a ready means of distinguishing between polluted and 

 unpolluted air, or of comparing the air of one district of a 

 city with that of another in regard to pollution. 



Nor is it at all likely that air containing 'oy per cent of 

 carbonic acid (but otherwise uncontaminated) is injurious 

 to health. Angus Smith found no ill-effects from air con- 

 taining 0*19 per cent of this gas, that is four times the 

 amount occurring in polluted air of the streets. Though 

 exhaustive enquiries have been made into the question of 

 the distribution and amount of the carbonic acid gas in the 



