AIR 



Newman 1 carried out some experiments upon the bacteria 

 in the air of bakehouses. The method used was to employ agar 

 plates and expose for 30 minutes, subsequently incubating for 

 22 hours at 37 C. While no accurate bacterial enumerations 

 could be made in this way valuable comparative data were 

 obtained. The average number of bacteria falling upon each 

 9*6 square inches (mean of three plates each) during the 30 

 minutes, was for underground bakehouses 600 800, for above- 

 ground bakehouses 200, while in the open air outside the 

 bakehouses it was 160. 



Haldane 2 , using a slightly modified form of Frankland's 

 method, carried out a number of bacterial enumerations in 

 factories and workplaces. The following table shows the 

 average results obtained for most of them : 



Average number of bacteria 

 per litre of air 



Number of - " ^ 



Factory or Workshop observations Bacteria Moulds Total 



Clothing Factories ... 7 7 4*5 n'5 



Tailoring Workshops ..* 7 TO 2 12 



Printing and bookbinding u 47 1*4 6'i 



Ropemaking 3 317 10 327 



The largest number of bacteria were present in the air of 

 the ropemaking premises. In one of the three factories 868- 

 bacteria per litre were found. 



These and other available data show clearly that the number 

 of bacteria in air depends upon the amount of dust stirred up 

 into the air. Little significance can be attached to the presence 

 of even large numbers of bacteria in the air if these bacteria are 

 derived from material which is unlikely to contain disease germs. 



The enormous number of bacteria in dust is illustrated from 

 the following two enumerations made by Gordon 3 of the dust of 

 the Debating Chamber of the House of Commons : 



(All per gramme) No. i No. 2 



Bacteria 10,000,000 100,000 1,000,000 



/?. coli loo IODO 100010,000 



B. enteritidis sporogenes 100 1000 100010,000 



Streptococci ... ... (none isolated) 10 1000 



i Public Health, 1902, vol. xv, p. 152. 



* Ventilation of Factories and Workshops, Departmental Committee, \st Report, 

 190 1. 



3 House of Commons (Ventilation}, Report, by Dr Gordon, 1906. 



