INDUSTRIAL FUMIGATION AGAINST INSECTS 51 



For the vacuum fumigation of tobacco (figs. 27 and 28) the follow- 

 ing dosages per 1,000 cubic feet are recommended : 10 Ethylene oxide- 

 carbon dioxide mixture, 60 pounds for 4 hours or 55 pounds for 15 

 hours for imported cigarette types, 50 to 55 pounds for 4 hours or 

 45 to 50 pounds for 15 hours for cigar-filler, 65 pounds for 4 hours 

 or 60 pounds for 15 hours for cigar-wrapper, and 45 pounds for 4 

 hours for manufactured cigars; liquid hydrocyanic acid, 5 pounds 

 for 4 hours or 4 pounds for 15 hours for imported cigarette types, 4 

 pounds for 4 hours or 3 pounds for 15 hours for cigar-filler, and 5 

 pounds for 4 hours or 4 pounds for 15 hours for cigar-wrapper tobacco. 



Flour xl 



For controlling insects in flour mills and reducing insect damage 

 to milled products, some form of fumigation is usually practiced. 

 Many millers are satisfied with one general fumigation a year, others 

 may supplement the general fumigation with local or spot fumiga- 

 tions, while some find it profitable to have several general fumiga- 

 tions a year in addition to a regular schedule of local fumigations. 



GENERAL MILL FUMIGATION 



General fumigations may be conducted by introducing all the gas 

 into the open space of the mill, by introducing all the gas into the 

 machinery, or by introducing a portion into the machinery and the 

 rest into the open mill space. Hydrocyanic acid, chloropicrin, and 

 methyl bromide can be used successfully in mill fumigation, although 

 hydrocyanic acid is used most extensively. 



FUMIGATION WITH HYDROCYANIC ACID 



Open-Space Method 



Preparing the Mill. — When all the fumigant is to be introduced 

 into the open mill space, it is necessary to dismantle the machinery 

 and make special preparations to insure a good kill. In addition to 

 the regular procedure for preparing a building for fumigation, the 

 directions given below should be followed : 



Before Stopping the Mill 



1. Shut off feed (wheat) at mixing bin. 



2. Continue running all machinery until material is emptied from spouts, 

 elevators, conveyors, rolls, sifters, reels, purifiers, feed dusters, suction trunk- 

 ing, and dust collectors. 



3. Remove elevator-boot slides and station men along the boots to keep stock 

 pulled out where belt cups will not carry it up. 



4. Meanwhile, hammer elevator legs, machinery, frames, tubular dust col- 

 lectors, and spouts with a rubber mallet or other device which will not bruise 

 or injure the equipment. 



After Stopping the Mill 



1. Open all machines, conveyor boxes, and flour bins. 



2. Remove covers of all conveyors, making certain that all dead-end spaces 

 are readily accessible. 



3. Thoroughly clean all conveyors, including dead-end spaces. 



4. Clean out accumulations from bottom section of the bran duster. 



10 See footnote 9. 



11 Further information on the fumigation of flour mills may be obtained from U. S. 

 Department of Agriculture Circular 390, revised, Flour-Mill Insects and Their Control. 



