6 HYDROCYANIC-ACID GAS AGAINST HOUSEHOLD INSECTS. 



action will begin at once, but the gas will not rise to any extent for a 

 few seconds or a quarter of a minute, and there is ample time to leave 

 the room quickly without danger of breathing the gas. Having 

 finished the garret or top floor, the operators should pass rapidly to 

 the next, and so on to the basement, making their exit through the 

 lower door to the street. 



Hydrocyanic-acid gas is lighter than air, and consequently rises; 

 therefore the operation must be begun at the top of the house. 



The house should be locked from the outside and, if necessary, a 

 warning sign put up to caution against entrance. 



The preparation of the different rooms, getting their cubic contents, 

 fixing the vessels, and preparing the charges, in a house of the size 

 indicated in the table given above, will take from two to three hours, 

 and this much time must be allowed for. The house should remain 

 closed, for the gas to become fidly generated and do its work, for 4 

 to 6 hours — preferably, however, and to get the greatest efficiency, 24 

 hours at least. 



Better results are claimed for a warm temperature, say 70° F. or 

 above, than in a temperature as low as 50° F. or below. Under 50° 

 most insects become torpid and the effective action of the chemical 

 will be diminished, especiallj^ in very low temperatures. 



At the close of the operation the doors may be opened and the 

 windows lowered or opened from the outside, and after an hour's 

 airing the house may be entered if no strong odor of gas is detected, 

 and opened up even more thoroughly, if possible, to allow a complete 

 airing for several hours. The house should not be reinhabited until 

 all traces of the odor of the gas have disappeared. This odor, as 

 stated before, has been compared to that of peach kernels. 



The contents of the generating jars should be poured into the 

 sewer trap or disposed of in some place where they will not be a 

 source of danger, and the jars thoroughly cleaned. 



THE CYANID AND (JAS A DEADLY POISON. 



In the use of hydrocyanic-acid gas for household fumigation it 

 must not be lost sight of for a single instant that one is dealing with 

 one of the most poisonous substances known, and that the accidental 

 eating of a small portion of cyanid wnll necessarily be fatal, and that 

 the inhalation of a few breaths of the gas will asphyxiate, and, if 

 rescue be not prompt, also have a fatal termination. It is much 

 better, therefore, if fumigation be contemplated, to put the work in 

 the hands of some one who has had experience, if such a person be 

 available; if not, to consider carefully all the recommendations and 

 precautions in this circular and become thoroughly familiarized with 

 them before undertaking the experiment. 



