2 ' CIRCULAR 369. U. S. DEPT. OF AGRICULTURE 



111 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 eafch 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. 



There is no reason why fumigation should be an expensive opera- 

 tion, for with simple equipment a few intelligent workers can be 

 quickly trained to fumigate most places with no more expense than 

 their time and the bare cost of the materials. 



