52 



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



6. Remove the adjustible 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 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 

 this gas may be used with good results. With the miller who does his 

 own fumigating the pot or barrel method is popular, but professional 

 fumigators prefer to use liquid hydrocyanic acid and avoid the labor 

 of handling barrels, water, and acid. Regardless of the method of 

 generation, . the gas is the same, and if the mill has been properly 

 prepared excellent results can be expected. 



Distribution of the Fumigant. — To obtain quick equalizing of 

 the fumigant, it should be evenly distributed throughout the mill, 

 except that floors containing more machinery than others should re- 

 ceive a heavier dosage. With all methods of application gas con- 

 centrations soon become uniform throughout the mill. 



Length of Exposure. — In the average mill heavy concentrations 

 of the gas can be maintained only for a very short period; hence 

 an exposure of from 10 to 24 hours is usually all that is practical. 



Machinery Piping Method 



Recently a method has been developed by which hydrocyanic acid 

 is applied directly into the milling machinery instead of into the 

 open mill space. A series of pipe lines connects each piece of ma- 

 chinery with a manifold outside the mill. Spray nozzles that open at 

 a set pressure deliver uniform quantities of fumigant to each piece 

 of equipment, and when the pressure is removed they close auto- 

 matically so that they cannot be clogged with milling stock between 

 fumigations. 



By applying the fumigant directly into the machinery, concentra- 

 tions high enough to penetrate the stock left in the milling equip- 

 ment are obtained with a smaller quantity of gas ; hence it is unneces- 

 sary to dismantle and clean out the machinery. The saving in time, 

 labor, and fumigant makes it possible to fumigate twice as often as 

 by the open-space method at no greater cost. 



Although it is unnecessary to follow the procedure recommended 

 for open-space fumigation, there are a few rules that should be 

 followed in preparing the mill for fumigation. 



