INDUSTRIAL FUMIGATION AGAINST INSECTS 



9 



stacks of bagged material should be avoided. In sections that are 

 divided into small compartments or storage rooms, the connecting 

 doors should be opened to allow a proper distribution of the gas. 

 Where sections of a floor are large, as in many metropolitan storages, 

 each section may be fumigated to better advantage as a single unit. 



Desirability of a High Temperature During the Fumigation 



It is desirable to maintain a fairly high temperature in the build- 

 ing during the fumigation. Insects are not very active at tempera- 

 tures below 60° F., and they become more or less dormant at 50° or 



Figure 11.— -Opening to elevator shaft sealed ready for fumigation in same 

 manner as the doorway in figure 10. In both cases the sealing was done at 

 the Naval Supply Depot, Naval Operating Base, Hampton Roads, Norfolk, Va. 



below. In the dormant state they are extremely difficult to kill with 

 fumigants. At 75° they are active and their susceptibility to the 

 gases increases as the temperature rises. For best results a tempera- 

 ture of at least 75°, and preferably somewhat higher, should be main- 

 tained throughout the fumigation. 



Effect of Wind Velocity 



The velocity of the wind during the exposure influences the effec- 

 tiveness of a fumigation. The fumigation should be conducted pref- 

 erably when there is no wind, since recent work has shown that in a 

 building of ordinary construction a strong wind will force a large 

 portion of the fumigant away from the windward side and so prevent 

 a uniform distribution of the gas. 



404673°— 42- 



