28 



CIRCULAR 3 6 9, U. S. DEPARTMENT OF AGRICULTURE 



Several t} T pes of metal vaults (fig. 28) can be purchased knocked 

 dovrn ready for assembling. These are excellent in every way. 

 Highly satisfactory vaults can be constructed of concrete, brick, or 

 hollow tile. The brick (fig. 29) and hollow-tile (fig. 30) vaults 

 should be finished inside with a layer of Keen's cement and 1 or 2 

 coats of paint. Wooden vaults with a metal lining are also popular. 

 It is possible to purchase 14-gage sheet metal cut up into sections 

 for constructing a vault 8 by 10 by 12 feet. When welded together, 

 the sections form an excellent gastight lining. 



The cheapest type of vault is made of wood. An efficient vault 

 can be constructed of two layers of 2-inch standard flooring sepa- 

 rated by a layer of heaA'y roofing paper. If the edges of each board 

 are painted with heavy white-lead paint just before the tongue and 

 groove are forced tightly together, the walls are even tighter. The 

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



Figuke 28. — 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. 



interior should be given 2 or 3 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. 



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. 30). The fumigant can then be run into the 



