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A PRACTICAL HOT AIR DISINFESTOR. 
By Major HAROLD ORR, O.B.E., M.B. (Toronto), C.A.M.C. 
(With 5 Text-figures.) 
The Hot Air Disinfestor herein described is the outcome of experiments 
undertaken in 1915, at the instigation of Colonel G. S. Rennie, C.M.G., then 
A.D.M.S., Canadians, Shorncliffe, in an effort to devise a satisfactory solution 
of the louse problem. 
During that period G. H. F. Nuttall, Quick Professor of Biology, Cambridge 
University, was engaged in a research on the life history of Pediculus humanus, 
and he very kindly communicated to me from time to time the results of 
his investigations. Early in 1915 he found that the louse and the nit were 
killed in 10 minutes in a dry atmosphere at 50° C. and 55° C. respectively. 
It seemed clear in view of this that dry heat properly applied would have 
many advantages over steam or sulphur di-oxide, the means then employed, 
and must eventually supersede them for practical disinfesting purposes on 
a large scale in armies. 
These advantages are obvious: 
1. Rapidity of action. It is at least twice as rapid as steam and six 
times as rapid as sulphur di-oxide. 
2. Simplicity in operation. 
3. No article of clothing (including leather) is in any way damaged. 
4. Clothing is not shrunken, creased or disfigured in any way. 
5. Clothes are delivered warm and dry. 
6. The fuel consumption is much lower than that of any other method 
of disinfestation. 
Since 1915, I have introduced and employed several types of disinfestors. 
That described in this paper is the one now used throughout the B.E.F. 
This disinfestor may be constructed in a few days’ time from material 
readily available in R.E. dumps in the forward areas. Five men, one of 
whom is a carpenter, are required. 
A sloping walled pit 5 feet deep (Fig. 1), measuring 7 ft. x 14 ft. at the 
top and 5 ft. x 10 ft. at the bottom is dug and the sides supported by trench 
revetting wire held in place by the usual steel pickets. Entrance to the pit 
is by a stairway at one side, and a tight-fitting door lined with corrugated 
