l6o 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 

 crock of earthenware or a wooden vessel and the water 



