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



impractical to use cold storage, and it is necessary to resort to fumi- 

 gation. This circular describes various methods by which products 

 in storage or the establishments in which they are manufactured 

 can be protected from insect attack b}^ 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). 

 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 



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 cyanide is ready to be 

 lowered into each barrel. 



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. 



GENERAL MILL OR WAREHOUSE FUMIGATION 



All mills, factories, warehouses, and storage rooms in which ma- 

 terial subject to insect attack is handled become infested at one time 

 or another and need a general fumigation. The managers of many 

 such places realize the importance of maintaining a clean plant and 

 fumigate one or more times a year as a general practice. Others, 

 fearing the trouble and expense, wait until conditions become so 

 bad that they are forced to shut down their mills for a thorough 

 cleaning and fumigation. 



