INDUSTRIAL FUMIGATION AGAINST INSECTS 



57 



One outlet hose from the machine is inserted in each of two elevator 

 legs, and the blower is operated for about 10 minutes. The hose is 

 then moved to two other elevator legs and the blower operated for 

 15 minutes. 



Windows in the mill should be kept open during the fumigation 

 and for 3 hours thereafter to allow the fumes to escape, 



Figure 38. — Apparatus for passing air through calcium cyanide dust in such a way 

 that the hydrocyanic acid gas evolved will be free from the dust. 



FUMIGATION OF FLOUR WAREHOUSES 



Warehouses containing flour, feed, or other cereal products often 

 become infested. In the average well-filled warehouse it is impossi- 

 ble, on account of the absorbent nature of these commodities, to obtain 

 a complete kill with any fumigant except methyl bromide. This 

 fumigant is effective in tight concrete or brick warehouses at a dosage 

 of 2 pounds per 1,000 cubic feet, but it is useless in loosely constructed 

 warehouses. It is not recommended, however, for the treatment of 

 milled cereal products intended for human consumption, owing to 

 the retention of large quantities of residual bromides by these 

 products. 



In loosely constructed warehouses hydrocyanic acid can be em- 

 ployed for general clean-up. purposes and to kill insects in the open 

 space and in the outer portions of bagged materials. A dosage of 



