320 RESPIRATION 



explosion. Practically speaking, afterdamp and smoke from fires 

 produce nearly the same effects, and require the same precautions. 

 A fire in the main intake of a mine is a most dangerous occurrence, 

 since the poisonous gas is apt to be carried all over the mine, and 

 to kill all the men in it. To afford a means of dealing with this 

 danger, the ventilating fans provided at British coal mines are 

 now so constructed that the air current can be at once reversed, so 

 as to drive back the smoke. 



Smoke from blasting may contain various poisonous gases, 

 along with CO 2 , according to the nature of the explosive. Some 

 explosives, such as guncotton, give much CO, and some very 

 little ; but all seem, in practice, to give some. Hence there is always 

 risk of CO poisoning where explosives are used in mines, unless 

 the proper precautions are taken. Black gunpowder, as used for 

 blasting, produces both CO and H 2 S ; and in the cases of gassing 

 it is often difficult to decide whether CO or H 2 S has been mainly 

 responsible for the effects. With explosives containing nitro- 

 compounds another and very serious danger is met with. When 

 these explosives detonate properly the nitrogen is given off as 

 nitrogen gas; but when they burn instead of detonating, the 

 nitrogen comes off as nitric oxide, along with CO instead of CO 2 . 

 In practice, owing to defective detonators or other causes, some 

 of the explosive is apt to burn instead of detonating. The nitric 

 oxide then passes into the air and combines with oxygen to form 

 yellow nitrous fumes. These have a somewhat irritant effect at the 

 time, but this is not sufficient to give proper warning of their 

 dangerous properties. The immediate effects are very slight. If, 

 however, enough of the mixture has been inhaled, the result is 

 that after a few hours symptoms of very severe lung irritation 

 appear, and finally oedema of the lungs and great danger to life. 

 I have found that exposure to the fumes from as little as .05 per 

 cent of nitric oxide in air may be fatal to an animal. This subject 

 will be referred to more fully below in connection with poisonous 

 gas used in war. 



Poisoning with CO in mines is so apt to occur, that a few words 

 may not be out of place as to the treatment of CO poisoning. The 

 symptoms and their cause have already been dealt with. The first 

 thing, is, of course, to get the patient out of the poisonous air. In 

 doing so, however, it is important to keep him well covered and 

 avoid in any possible way exposing him to cold. For some reason 

 which is at present not clear, a man suffering from CO poisoning 

 gets much worse on exposure to cooler and moving air, as in the 



