160 FUMIGATION METHODS 
6. A door and several windows or other open- 
ings should be adjusted so they can be opened from 
‘the outside to permit the escape of the gas after 
fumigation is completed. Where convenient several 
windows on each floor should have the top sash ar- 
ranged so they can be lowered by means of a rope 
from the outside. In this manner ventilation is per- 
fect and the gas soon escapes. 
7. A special watchman should be detailed to look 
after the fumigation and guard the premises while the 
gas is enclosed and after it is released. 
8. In buildings where several rooms or floors are 
fumigated at the same time, each room or floor should 
be shut off from the other as much as possible. Where 
open stairways lead from one floor to another, it will 
be necessary to cover them temporarily with light 
boards, over which can be thrown old bags, sacks, 
blankets, etc. Care should be taken not to blockade 
the stairway so the operator cannot readily escape 
when the gas is generated. By closing the doors be- 
tween the rooms and covering the stairways the gas is 
kept at a very uniform density in each room for a 
longer period. 
Making the gas.—The chemicals used for making 
hydrocyanic acid gas are potassium cyanide, sulphuric 
acid and water. Special directions for combining these 
chemicals for generating the gas are given in Chapter 
II. ‘These instructions should be carefully studied and 
followed specifically, as the process will admit of no 
guesswork. ‘The cautions cited should be heeded and 
considered at all times. The acid is first placed in a 
ercck of earthenware or a wooden vessel and the water 
