IQ CIRCULAR 369, U. S. DEPT. OF AGRICULTURE 



it will be impossible to maintain a strong concentration of any gas 

 for very long, and a quick-acting gas is the only kind that will be 

 effective. Hydrocyanic acid is the only gas available that will kill 

 quickly. 



QUANTITY OF FUMIGANT NEEDED 



The quantity of fumigant to be used will vary according to the 

 length of exposure, the temperature, the tightness of the building, 

 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. Since most 

 commercial establishments are not airtight, the natural leakage from 

 a building is often great enough to prevent a killing concentration 

 from ever being attained, particularly if it takes considerable time 

 to reach that concentration. From some buildings fumigants escape 

 so rapidly that it is not practical to fumigate them. In buildings 

 that can be fumigated with reasonable expectation of success, the 

 best results are obtained by releasing the entire dosage at the begin- 

 ning of the fumigation. 



A uniform concentration will be obtained more rapidly if the fumi- 

 gant is distributed equally throughout the building. When using 

 fighter-than-air gases it is not necessary to place the heaviest dosage 

 on the lower floors, since gas concentrations tend to become equalized 

 in all parts of the building shortly after the fumigant is introduced. 



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. 



VENTILATING THE BUILDING AFTER FUMIGATION 



After the fumigation the building should be aired out by opening 

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

 outside. If this is not possible, the windows should be opened from 

 the inside by workmen wearing gas masks and preferably Avorking 

 in pairs to avoid accident. A few windows on the top and bottom 

 floors and on each side of the building should be opened first to 



