INDUSTRIAL FUMIGATION AGAINST INSECTS 9 



machinery, in feed bins, or in any part of the building should also be 

 removed and sold or destroyed before fumigation. 



Commodities in warehouses or storage rooms should be so arranged 

 as to provide the maximum circulation of the fumigant; large, solid 

 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 

 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 effective- 

 ness of a fumigation. The fumigation should be conducted preferably 

 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. 



EFFECT OF LIGHT OR DARKNESS 



Light and darkness have no appreciable effect upon the results of a 

 fumigation. Although insects are more quickly affected while they 

 are active, entirely satisfactory results follow the application of a 

 fumigant during the day when the insects, such as cockroaches and 

 bedbugs, are chiefly resting in hiding places. In general, professional 

 fumigators work at times most convenient to the establishment to 

 be fumigated without thought of light or darkness. In the case of 

 an insect, such as the cockroach, that forages in the dark, more in- 

 dividuals may be killed by a night fumigation if the daytime hiding 

 places are in wall spaces difficult of gas penetration. Usually, how- 

 ever, hiding places of insects in commercial plants are easily pene- 

 trated by fumigants, and the time of day the fumigant is applied is 

 therefore unimportant. 



CHOICE OF A FUMIGANT 



In choosing a fumigant several factors must be taken into con- 

 sideration. If the building is modern and very tight, several fumi- 

 gants can be used with success, and a choice can be governed by such 

 items as cost, efficiency, availability, safety, and effect upon the com- 

 modity to be fumigated. If the building is not particularly tight. 



4964°— 37 2 



