INDUSTRIAL FUMIGATION AGAINST INSECTS 



29 



floor, walls, and roof should be of the same tight construction. The 

 interior should be given two or three coats of any good paint. An 

 aluminum paint is sometimes used to advantage. 



All types of vaults should be equipped with a refrigerator or safe 

 type of door, well gasketed to make it gastight. 



A ventilating system capable of quickly removing the fumigant 

 from the vault after the fumigation is essential. If the vault is set 

 up inside a building, the ventilating stack must extend outside the 

 building and preferably above the roof. 



It is sometimes desirable to install an electrical heating unit, con- 

 trolled by a thermostat, so that a constant high temperature can be 

 maintained throughout the fumigation. The heating unit should not 

 be operated, however, while inflammable fumigants are being used. 



Figure 27. — Two types of metal vaults such as can be purchased or built according to 

 space and commodity need. These vaults are used for treating the day's arrival of 

 fur coats offered for summer storage. After an overnight fumigation in these vaults 

 the furs are removed to large permanent storage vaults. 



For applying the fumigant several different methods can be used. 

 For heavier-than-air gases a shallow evaporating pan or trough 

 should be installed near the ceiling of the vault, with a feed pipe ex- 

 tending outside (fig. 29). The fumigant can then be run into the 

 evaporating pan by gravity or compressed air. If liquid hydro- 

 cyanic acid or any of the commercial mixtures is to be used, a short 

 piping system with one or more spray nozzles can be installed (figs. 

 20,21, and 26). 



USE OF FUMIGANTS SUITABLE ALSO FOR LARGE SPACES 



Hydrocyanic acid, chloropicrin, and mixtures of carbon dioxide with 

 ethylene oxide, methyl bromide, and methyl formate are all suitable 

 for vault fumigation, and they can be used in the manner described 

 for the fumigation of large spaces. The method selected for gener- 

 ating hydrocyanic acid will depend largely upon the preference of 

 the operator. Any of the previously described methods is suitable. 



