USE OF GASES AGAINST HOUSEHOLD INSECTS 451 



the floors below in succession, treating each in the same 

 manner. Although it took about one hour to treat each 

 floor, not the slightest inconvenience or annoyance was 

 experienced by the men from the gas on the floor or floors 

 above. There is another advantage in this method. 

 Where the sun shines in windows the strips of paper, 

 although we used three thicknesses and soaked them 

 thoroughly, were apt to dry and curl away from the cracks 

 if left too long. By treating a floor as soon as ready, we 

 obviate this difficulty and get the full effect of the gas. 



Points that should be kept in mind. — It is claimed that 

 better results will be obtained when the temperature of 

 the rooms is maintained at 70 degrees F. or above than at 

 50 degrees or below. Most insects become inactive and 

 torpid at temperatures below 50 degrees and in this condi- 

 tion are apparently less easily affected by the gas. For 

 this reason the fumigation had probably best be done in 

 the summer if possible. 



In pouring the acid great care should be taken to pre- 

 vent it from spattering on the hands and face. 



The cyanide, to give most complete chemical reaction, 

 should be broken up into pieces about the size of hickory 

 nuts. This is best done on a hard brick or cement pavement. 

 The hands should be protected with gloves and washed at in- 

 tervals to remove the fine particles of cyanide from the skin. 



The doors of the house under treatment should be locked 

 and conspicuous signs of danger should be placed at the 

 main entrances. 



The work should be done by a calm, thoughtful, and 

 careful person — best by one who has had some experience. 



The gas is lighter than air and one should always start 

 in the rooms at the top of the house and work down. 



