VENTILATION. 377 



mental, and less power of resisting disease; the ill effects 

 may not show themselves at once, and may accordingly be 

 overlooked, or considered scientific fancies, by the careless; 

 but they are there ready to manifest themselves neverthe- 

 less. In order to have air to breathe in a fairly pure 

 state every man should have for his own allowance at least 

 23,000 liters of space to begin with (about 80ft cubic feet) 

 and the arrangements for ventilation should, at the very* 

 least, renew this at the rate of 30 liters (one cubic foot)' 

 per minute. The nose is, however, the best guide, and it 

 is found that at least five times this supply of fresh air is 

 necessary to keep free from any odor the room inhabited by 

 one adult. In the more recently constructed hospitals, as 

 a result of experience, twice the above minimum cubic space- 

 is allowed for each bed in a ward, and the replacement of 

 the old air at a far more rapid rate is also provided for. 



Ventilation does not necessarily imply draughts of cold 

 air, as is too often supposed. In warming by indirect radi- 

 ation it may readily be secured by arranging, in addition to- 

 the registers from which the warmed air reaches the room, 

 proper openings at the opposite side, by which the old air 

 may pass off to make room for the fresh. An open fire in 

 a room will always keep up a current of air through it, and 

 is the healthiest, though not the most economical, method 

 of warming an apartment. 



Stoves in a room, unless constantly supplied with fresh air 

 from without, dry its air to an unwholesome extent. If no- 

 appliance for providing this supply exists in a room, it can 

 usually be got, without a draught, by fixing a board about, 

 four inches wide under the lower sash and shutting the 

 window down on it. Fresh air then comes in by the open- 

 ing between the two sashes and in a current directed 

 upwards, which gradually diffuses itself over the room with- 

 out being felt as a draught at any one point. In the 

 method of heating by direct radiation, the apparatus em- 

 ployed provides of itself no means of drawing fresh air into 

 a room, as the draught up the chimney of an open fireplace 

 or of a stove does; and therefore special inlet and outlet 

 openings are very necessary. Since few doers and windows, 



