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CIRCULAR 8 6 9, U. S. DEPARTMENT OF AGRICULTURE 



A power sprayer has been especially designed for use in tobacco 

 warehouses. This machine has a blower that will deliver approxi- 

 mately ^.400 cubic feet of air per minute at an initial velocity of 

 about 5,700 feet per minute. Such a spray machine will blow finely 

 atomized spray 100 feet or more, and reasonably good coverage can 

 be obtained in open warehouses, even with a breeze of 6 to 7 miles an 

 hour (fig. 11) . The spray should be a moderately fine mist. A spray 

 that will hang in the air for not less than 5 minutes or more than 15 

 minutes is most satisfactory. 



Figure 11. — Applying pyrethrum-oil space spray in a warehouse containing flue- 

 cured tobacco. 



Fire-insurance underwriters have approved the use of pyrethrum- 

 oil spray in tobacco warehouses when prepared and used as directed. 

 Although the flash point of the oil used in these sprays is approxi- 

 mately 175° F., such oil is moderately flammable and might be ex- 

 plosive under certain conditions. Only electric spray machines should 

 be used. Sparkproof motors and switches and heavy-duty rubber- 

 jacketed extension cord containing a grounding wire should be used 

 on all sprayers. 



All precautions recommended by the interested fire insurance com- 

 panies should be carefully followed. 



Closed-Type Warehouses 



The closed-type warehouse differs from the open-type in that it can 

 be sealed for fumigation. Closed warehouses usually afford better 



