RESPIRATION 307 



gas may be used very easily for purposes of suicide or even 

 murder. The great majority of accidental deaths from poisoning 

 by lighting gas have been in bedrooms, owing to the gas being in 

 some way left turned on after being extinguished. In 1899 ^ 

 Departmental Committee of which I was a member reported on 

 the influence of the use of water gas in connection with poisoning 

 by lighting gas, and I investigated the conditions under which 

 poisoning may occur in bedrooms.^ 



It might be supposed that the sense of smell would always give 

 warning of an escape of lighting gas in a room. On going into a 

 room in which gas is escaping one notices the smell at once, and 

 long before sufficient gas is present to cause any symptoms of 

 poisoning; but a person inside the room when the escape begins 

 may quite probably never notice it. The reason for this is that 

 the sense of smell for any particular substance becomes fatigued 

 very rapidly, and if the proportion of the odoriferous substance in 

 the air is only very gradually increased the smell is never noticed. 

 In this way an escape of gas in a bedroom is often unnoticed. 



When a continuous escape of gas occurs in a room, the per- 

 centage of gas in the air goes on increasing until the rate of es- 

 cape through walls, roof, etc., balances the rate of inflow of gas. 

 In any ordinary room the walls, roof, and floor are permeable to 

 air, and, if any cause such as pressure of wind or diff'erence of 

 temperature between inside and outside tends to produce air 

 currents in and out of the room, the flow of air is surprisingly 

 free. If, for instance, the door and windows are closed and all 

 visible chinks pasted up, it will be noticed that when a fire is lit 

 the chimney draws just as well as before. Large volumes of air 

 are passing up the chimney, and this air comes in through the 

 walls, roofs, etc. Brick and stonework, for instance, are fairly 

 permeable to air, as can easily be shown by suitable means. Small 

 rooms in a dwelling house do not require artificial ventilation, 

 provided the passages, etc., are well ventilated, since the ratio of 

 surface to cubic capacity is high, so that ventilation through the 

 surfaces of the room counts for more in relation to the cubic space 

 per person in the room. 



It will thus be readily seen that what happens in a room when 

 gas escapes continuously will depend on various circumstances, 

 such as the diff'erence in temperature between inside and outside, 

 the presence of a fire or of central heating by warm air, the 



" Report of the Water-gas Committee, Pari. Paper, 1899. Appendix i. 



