6 FARMERS’ BULLETIN 699. 
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 con- 
tents, placing the vessels, and preparing the charges, in a house of the 
size indicated in the foregoing table, 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 fully generated and do its work, 
for from 4 to 6 hours at least—preferably, however, and to get the 
greatest efficiency, for 24 hours. 
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, especially 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 GAS A DEADLY POISON. 
In the use of hydrocyanic-acid gas for household fumigation we 
must not for a single instant lose sight of the fact that we are dealing 
with one of the most poisonous substances known; that the accidental 
eating of a small portion of cyanid will necessarily be fatal; and | 
that the inhalation of a few breaths of the gas will asphyxiate, and, 
if rescue be not prompt, 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 bulletin and become thoroughly familiarized with 
them before undertaking the experiment. 
While the writers thus strongly emphasize the dangerous and even 
fatal qualities of this gas when breathed by human beings, it is 
worthy of remark that in the thousands of operations which have 
been carried on with this gas in different parts of the world only 
