128 



PRIXCIPLES OF BACTERIOLOGY 



FIG. 66 



This generator is cheap and efficient, but considerable care should 

 be observed in operating it, as there is a tendency to throw out some 



formalin before the gas begins to be evolved. 

 This is easily avoided by using care in the 

 proper application of the heat. These 

 generators have now been in use for three 

 years by the New York Health Department, 

 and have given complete satisfaction. 



As a result of the investigations under- 

 taken in the Department of Health labora- 

 tories on the use of formaldehyde as a 

 disinfectant, and a consideration of the 

 work of others, the conclusions reached by 

 us may be summarized as follows: 



1. DISINFECTION OF INFECTED DWELL- 

 INGS. Exposed surfaces of walls, carpets, 

 hangings, etc., in rooms may be super- 

 ficially disinfected by means of formalde- 

 hyde gas. All apertures in the rooms 

 should be tightly closed and from six to 

 twelve ounces of formalin or its equivalent 

 used to generate the gas for each 1000 

 cubic feet. The time of exposure should 

 be not less than four hours, and a suitable 

 A, steam chamber; B, formalin appara tus should be employed. The tem- 



chamber: C, steam supply; D, d rip ; ,, / i i i i 



E, inlet for formalin; F, outlet tor perature of the apartment ^ should be as 

 formaldehyde. high as possible, and certainly not below 



50 F. With even lower temperature dis- 

 infection is possible, but larger amounts of formalin must be used. 

 When generated very rapidly the formaldehyde gives much better 

 results than when given off slowly. 



Under these conditions spore-free bacteria and the contagion of the 

 exanthemata are surely destroyed when freely exposed to the action 

 of the gas. Spore-bearing bacteria are not thus generally destroyed; 

 but these latter are of such rare occurrence in disease that in house 

 disinfection they may usually be disregarded, and, if present, special 

 measures can be taken. 



The penetrative power of formaldehyde gas in the ordinary room, 

 at the usual temperature, even when used in double the strength neces- 

 sary for surface disinfection, is extremely limited, not passing, as a 

 rule, through more than one layer of cloth of medium thickness. Arti- 

 cles, therefore, such as bedding, carpets, upholstery, clothing, and the 

 like should, when possible, be subjected to steam, hot air, or formal- 

 dehyde disinfection in special chambers constructed for the purpose. 

 If not, they must be thoroughly exposed on all sides. 



2. DISINFECTION OF BEDDING, CARPETS, UPHOLSTERY, ETC. Bed- 

 ding, carpets, clothing, etc., which would be injured by steam, may be 

 disinfected by means of formaldehyde gas in an ordinary steam disin- 



