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



the amount of absorption and adsorption by the commodities to be 

 fumigated and by the walls and floors of the building itself, and the 

 insect to be eradicated. The shorter the exposure, the lower the 

 temperature, the looser the construction of the building, the greater 

 the absorption and adsorption, and the more resistant the insect, 

 the greater must be the dosage. The fumigator must exercise his 

 own judgment in each case. 



APPLYING THE FUMIGANT 



The fumigant should be applied in such a way that a maximum 

 concentration will be obtained as quickly as possible. If the concen- 

 tration is slow in building up, the natural leakage from a building 

 is often great enough to prevent a killing concentration from ever 

 being attained. 



TVhere it is desirable to maintain a heavy concentration over a long 

 period, it may be necessary to use a combination of fumigants, one 

 that will act quickly and another that will work more slowly and 

 will serve to maintain a lethal concentration for an extended period. 

 This is of particular importance in the fumigation of flour mills 

 and similar structures where a deep penetration of the fumigant 

 is essential. 



The distribution of the fumigant will depend upon the structure 

 of the building and the nature of the gas. If a lighter-than-air gas 

 is used, the heaviest dosage must be placed on the lower floors, and 

 if the flooring has many cracks and apertures, a much heavier 

 dosage than usual must be placed on the lower floors. In some cases 

 floors are so poorly constructed or so worn that the entire dosage 

 should be applied on the first floor. 



If the fumigant is not applied from the outside, the fumigating 

 crew should be supplied with gas masks having canisters adapted for 

 the gas that is to be used. Each operator should be familiar with 

 the entire plan of procedure as well as with his own particular job. 

 One man should be delegated to watch the others and to give aid in 

 case anyone gets into trouble. Help given at the right time will 

 prevent possibly fatal accidents. 



Before the fumigation is started, the building should be thoroughly 

 searched to make sure that no workmen or visitors are inside. Dur- 

 ing the fumigation all entrances to the building should be kept 

 locked and usually guarded by watchmen. Placards warning people 

 to keep out should always be tacked on all doors. 



After the fumigation the building should be aired out by opening 

 windows and doors. If possible, these should be opened from the 

 outside. This is sometimes done by pulling open the windows on the 

 upper floors by means of cords extending from a screw eye attached 

 to the sash and long enough to be tied to the iron grille of the base- 

 ment windows. If some such arrangement is not feasible, the win- 

 dows can be opened from the inside by workmen wearing gas masks. 

 In order to avoid accidents, two men should always work together 

 when ventilating a building. It is important that the watchmen be 

 instructed to prevent anyone from entering the building while it is 

 being ventilated. A large proportion of the fatalities connected 

 with fumigation have been due to criminal neglect on the part of 

 watchmen. 



