NO. 2$ INFLUENCE OF ATMOSPHERE ON HEALTH 1 5 



percentage of oxygen. Thus the aeroplanist may become seized with 

 altitude sickness from oxygen want, while his gas-engine continues to 

 carry him to loftier heights. 



The partial pressure of oxygen in a mine at a depth of 3,000 feet 

 is considerably higher than at sea-level, and if the percentage is 

 reduced to 17, while the firing of fire-damp and coal dust is impos- 

 sible, there need be in the alveolar air of the lungs no lower pressure 

 of oxygen than at sea-level. Thus the simplest method of preventing 

 explosions in coal mines is that proposed by J. Harger, 1 viz., to venti- 

 late them with air containing 17 per cent of oxygen. There is little 

 doubt that all the great mine explosions have been caused by the 

 enforcement of a high degree of chemical purity of the air. In old 

 days when ventilation was bad there were no great dust explosions. 

 Air. W. H. Chambers, general manager of the Cadeby mine, where 

 a recent disastrous explosion occurred, with the authority of his 

 great and long practical experience of fiery mines, told us that the 

 spontaneous combustion of coal and the danger of explosion can be 

 wholly met by adequate diminution in ventilation. The gob-fires 

 can be choked out while the miners can still breathe and work. The 

 Coal Mines Regulation Act enforces that a place shall not be in a 

 fit state for working or passing therein, if the air contains either 

 less than 19 per cent of oxygen, or more than 1.25 per cent of 

 carbon dioxide. A mine liable to spontaneous combustion of coal 

 may be exempted from this regulation by order of the Secretary of 

 State. It is also provided that any intake airway shall not be 

 deemed to be fit for persons travelling thereon, if the average per- 

 centage of inflammable gas found in six samples of air. taken at 

 intervals of not less than a fortnight, exceeds 1.25 per cent. Work- 

 men must be withdrawn from any working place, if worked with 

 safety-lamps, if the percentage of inflammable gas is found to be 2.5 

 per cent or upward, or if worked with naked lights, 1.25 per cent 

 or upward. 



These regulations impel the provision of such a ventilation cur- 

 rent that the percentage of oxygen is sufficient for the spread of dust 

 explosions along the intake airways, with the disastrous results so 

 frequently recorded. If the mine were ventilated with air contain- 

 ing 17.5 per cent of oxygen in sufficient volume to keep the miners 

 cool and fresh, not only would explosions be prevented but the mines 

 could be safely illuminated with electric or acetylene lamps, and 



1 Coal, and the Prevention of Explosions. Longmans, Green & Co., London, 



