122 THE WONDERFUL HOUSE THAT JACK HAS 



careless enough to sit in a draught. As a matter of 

 fact, if enough windows had been opened to cause a 

 good circulation of air, the breathing supply would 

 have been kept pure and probably illness might not 

 have resulted. Free circulation of air in a room can 

 usually be had without forcing any of its occupants to 

 sit in a draught. The danger from such exposure 

 seems to be very generally understood, but if many 

 people were only half as fearful of breathing unclean 

 air as they are of being in draughts, vigorous health 

 would certainly be much more common. 



But if we cannot see the filth in the air, is there any 

 way of telling whether the atmosphere we are in is 

 fit to breathe? Certainly the sense of smell cannot 

 be trusted. The noxious odor is quickly noticed when 

 we first enter a room where the air is impure. How- 

 ever, if we remain in such atmosphere for a time, or 

 have been one of the number present from the be- 

 ginning, our nostrils gradually become used to the 

 disagreeable odor and cease to give warning of the 

 danger. The best plan is to get into the habit of 

 noticing whether the arrangements for ventilating a 

 room are such as will keep the air pure. How large 

 a room is and whether there are openings for the air 

 to get in and out, can usually be told at a glance. 



An artificial light usually consumes several times as 

 much air as each person. An oil lamp vitiates the 

 air of a room much faster than an ordinary gas jet. 

 The burning of a mantle gas-jet makes the air impure 



