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



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 and chloropicrin 

 can be used successfully in mill fumigation, although the former is 

 used more extensively. 



Fumigation With Hydkocyanic 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. 



5. Clean all elevator belting that may be webbed ; drag spouts of same. 



6. Remove the adjustable feed gage above grinding rolls and clean out 

 accumulations above rolls and feeders. 



7. Examine tubular dust collectors and clean out all accumulations. 



8. Clean out suction trunks, conveyors, and dust-collector systems. 



9. Open dust collectors, back drafts, main trunks, and hand openings. 



10. Loosen all sifter doors to permit entrance of gas during fumigation ; 

 remove sieves and stack on floor. 



11. Leave every machine open ; also all hand openings to spouts, elevator 

 legs, etc. 



12. Remove and burn all infested materials accumulated in cleaning the mill. 



13. All infested lots of flour and other milled products should be removed 

 (or reconditioned) before cleaning the mill. These products should not be 

 returned. 



14. If the above procedure is followed, no accumulation of more than 1 inch 

 in depth will be present in the mill. 



15. Special attention should be given to the cleaning of the dead spouts and 

 dead spaces in corners of spouts and machines. 



16. Remove all bags and other materials used to plug spouts. 



17. Seal roof ventilators or replace mushroom-shaped cap with a tight 

 metal cap. 



Dosage and method of generation. — In general, a dosage of 8 

 ounces of liquid hydrocyanic acid or its equivalent per 1,000 cubic 

 feet of space has been found most satisfactory for flour-mill fumi- 

 gation. All the methods that have been described for generating 



