INDUSTRIAL FUMIGATION AGAINST INSECTS 



17 



Therefore, when the generator is moved, the contents are shaken up 

 and additional small quantities of gas may be given off. For this 

 reason the operator should breathe as little as possible or use gas 

 masks while handling the barrels and should not hold his head over 

 the barrel. 



The residue, which is poisonous, can be disposed of by dumping 

 it down a street drain (fig. IT) or by pouring it into a hole in the 

 ground and covering it with soil. 



THE LIQUID METHOD 



Liquid hydrocyanic acid is a volatile, colorless liquid which boils 

 at 79° F. It is marketed in cylinders containing 30 or 75 pounds. 

 On exposure to air it 

 gives off the same gas 

 that is generated by 

 mixing sodium cyan- 

 ide with sulphuric 

 acid and water. In 

 the hands of an ex- 

 pert fumigator it is 

 an almost ideal fumi- 

 gant for use in large 

 enclosures. 



After a building 

 has been prepared for 

 fumigation, the gas is 

 applied entirely from 

 the outside (figs. IS 

 and 19). The cylin- 

 ders containing the 

 1 i q u i d hydrocyanic 

 acid are lined up near 

 the building, and the 

 fumigant is forced in 

 by compressed air. A 

 proper distribution of 

 the gas within the 

 building is obtained 

 by means of lines of 



pressure rubber tubing or metal piping equipped with spray nozzles. 

 A gas mask should be worn or close at hand. 



Figure 17. — Men carrying containers from a warehouse 

 to empty into a city drain the residue from a hydro- 

 cyanic acid gas fumigation. 



Piping the Building 



In small enclosures the gas can be distributed through rubber tub- 

 ing, but in large warehouses or mills it is desirable to install a per- 

 manent system of piping. This may be constructed of iron, brass, or 

 copper. The iron piping is the least expensive, but, owing to its 

 tendency to rust and cause clogging of the spray nozzles, it is rarely 

 used. Either brass or. copper tubing is recommended. A flexible 

 copper tubing three-eighths inch in diameter (fig. 20) costs about 6 

 cents a foot. Since it can be readily bent, elbow fittings are unneces- 



430°— 35 3 



