CONTROL OF INSECTS IN TOBACCO 



27 



EQUIPMENT AND PROCEDURE 



Vacuum fumigation equipment consists of a pair of steel chambers 

 strong enough to withstand considerable pressure, a pump of suit- 

 able size to evacuate the chambers, a volatilizer for the fumigant 

 (for use in cool weather), and recording gages. Loading platforms 

 and conveyors facilitate the handling of the tobacco. The chambers 

 vary widely in size, most of those in commercial use ranging from 400 

 to 3,000 cubic feet. In some of the larger units each chamber has a 

 capacity of more than 30 hogsheads. 



The tobacco to be fumigated is placed in the vacuum chamber, the 

 door is closed, and the air is pumped out until a vacuum of 28 to 29 

 inches is registered on a standard mercury gage (fig. 20) . The degree 

 of vacuum obtainable varies from day to day with the barometric pres- 

 sure, but any vacuum of more than 28 inches is usually satisfactory. 

 The proper dosage of fumigant is determined by weighing. The cylin- 

 der or drum of fumigant is placed on a platform scales and connected 

 to the intake line of the chamber. When a valve is opened the gas is 

 sucked into the chamber and drawn all through the tobacco by the 

 vacuum. At the end of the exposure period the gas is pumped out of 

 the chamber and vented above the roof of the building. Air is then 

 admitted to restore normal pressure in the chamber. This air is ex- 

 hausted by pumping and air is again admitted. This procedure — 

 called air washing — is usually performed twice with each lot of 

 tobacco. 



The manufacturers of vacuum-fumigation equipment can supply 

 estimates and specifications to meet the needs of individual factories 

 or warehouse operators. 



Figure 20. — Vacuum chambers for fumigating tobacco. 



