FRESH AIR AND EFFICIENCY 277 



comes unhealthy. Any practicable increase in the 

 floor space would be, per se, no material remedy for 

 the bad air conditions. For with an additional 10 

 square feet of floor area the air would reach the same 

 standard of impurity after a further few minutes; and 

 if the air is only changed once in every hour the re- 

 spiratory carbon dioxide would reach 0.13 per cent at 

 the end of the hour, and the associated physical con- 

 ditions would render the air unhealthy. Therefore, 

 short of an impossible allowance of sleeping space, 

 frequent air-renewal is the sole means of keeping the 

 air fairly fresh, and therefore capable of maintaining 

 health and vigour. For this, opposite open windows, 

 as many as possible, according to weather conditions 

 (and always at least two diagonally opposite ones), 

 are necessary. If there are hopper windows, every 

 other one on both sides should be permanently fixed 

 in an open position. These remarks apply whatever 

 other ventilation expedients have also been adopted. 

 But, notwithstanding the fear of punishment for dis- 

 obedience, orders are always most effective, from the 

 standpoint of results, when all concerned are informed 

 upon their object and importance; and the practice of 

 the open window depends very largely indeed upon 

 the formation of the conviction that leads to practice, 

 and thus to the formation of habit. And so this sub- 

 ject has generally been introduced among those on 

 which the soldier has been appealed to by the medical 

 officer. 



Unfortunately, efforts to promote the better ventila- 

 tion of quarters by night have been seriously inter- 

 fered with in many camps by the lighting orders 

 necessitated by enemy bombing raids; for the darken- 

 ing of an open window by closely covering it with 

 a heavy curtain, &c., seriously discounts its value for 

 ventilating purposes. 



