6 



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



great enough to allow for the loss through poor construction of the 

 building, absorption by the contents of the building, and adverse 

 weather conditions. The fumigant must also be properly applied 

 and distributed. The exposure must be long enough to permit maxi- 

 mum penetration and killing effect. 



Figure 7. — Doors to warehouse, and transom, sealed with old advertising posters 

 cut into strips. Latticed warehouse doors in warm climates can be effectively 

 sealed with three or four thicknesses of such material. 



Preparing the Building for Fumigation 



It is essential that the building be made as nearly gastight as pos- 

 sible. A modern concrete building having windows with steel frames 

 is excellent for fumigation purposes, since little effort is needed to 

 make it reasonably gastight. Doors leading to the outside should be 

 sealed (fig. 7). Ventilators on the roof (fig. 8) or outside walls 

 should also be sealed over, and any windows that are not tight 

 should be sealed around the edges. 



