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



them. If cold-storage facilities are available, such commodities can 

 be protected from insect damage by holding them, at temperatures 

 below 45° to 50° F. Many times, however, it is impossible or imprac- 

 tical to use cold storage, and it is necessary to resort to fumigation. 2 

 This circular describes various methods by which products in storage 

 or the establishments in which they are manufactured can be protected 

 from insect attack by the use of fumigants. 



In the protection of stored commodities four methods of fumiga- 

 tion are in common use: (1) The general or large-scale fumigation 

 of warehouses and mills (fig. 1), (2) vault fumigation (fig. 2), 

 (3) bin fumigation (fig. 3), and (4) vacuum fumigation (fig. 4). 



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Figure 1. — Interior view in flour mill ready for fumigation with hydrocyanic acid 

 gas generated by the barrel method. The eight barrels containing the acid- 

 water mixture stand in galvanized-iron washtubs, and a sack of sodium cya- 

 nide is ready to be lowered into each barrel. Men lowering these sacks into 

 the barrels, or working in any capacity around this or similar operations, 

 should wear an approved gas mask and oiled leather gloves. 



Each method is adapted to a certain type of work and will be dis- 

 cussed separately. In most industries a combination of two or more 

 of these methods can be used to advantage; and sometimes special 

 methods, such as fumigation under tarpaulins (fig. 5) or the treat- 

 ment of the individual pack of a commodity (fig. 6), are developed. 



2 The Division of Insecticide Investigations of this Bureau states (August 1942) that 

 there are ample supplies of all the fumigants mentioned in this circular except carbon 

 tetrachloride and ethylene dichloride. Owing to war priorities these two will be available 

 for fumigation purposes only in restricted amounts unless the War Production Board can be 

 convinced that their use is essential to the conduct of the Avar. There may develop a 

 shortage of copper tubing for liquid hydrocyanic acid fumigation of large buildings and of 

 steel for the construction of vacuum fumigators. 



