.8 FAEMEES' BULLETIjST 709, 



obstacle in the way. All felt materials are extremel}^ porous and are 

 unsatisfactory for use in packing around doors, etc., as they are 

 often used. Hea%^, hard-rolled wrapping* paper, or 2-ply roofing 

 paper of certain brands, is actually gas-tight and may be used as a 

 lining material between layers of boarding in the construction of 

 fumigation rooms and for pasting over cracks where necessary to 

 tighten a room. Ordinary matched flooring or ceiling alone is very 

 far from being tight. 



MAKING A FUMIGATION ROOM OH BIN. 



One of the simplest satisfactory containers for fumigation on a 

 small scale is a water-tight barrel. This may be used for the treat- 

 ment of peas, beans, etc., or for other materials that may be con- 

 tained therein. The top of the barrel is best closed by spreading 

 heavy wrapping paper, double thickness, over and around the top 

 and tying it tightly. 



In making a special room or bin for fumigation work it is best 

 to put on one layer of boards of uniform thickness, flooring or 

 ceiling, and then to cover this with a layer of heavy building 

 paper, tarred paper, or similar material, which is folded or bent 

 to fit into the corners and then is laid so as to overlap 3 or 4 inches 

 and the edges securely pasted or cemented together so as to make 

 it practically one solid piece of gas-tight covering. A final layer of 

 boarding running in an opposite direction to the first is applied to 

 protect the paper from being broken as it is used. Windows should 

 be small and aiTanged for convenient opening from the outside for 

 ventilation, and door bearings should be against paper surfaces 

 instead of cloth or felt. In such a roonj or bin fumigation may be 

 practiced with the maximum of efficiency and economy. The appli- 

 cation of an ineffective amount of t\ni fumigant is practically a waste 

 of all the material used and often also a Avaste of the products inef- 

 fectively treated. 



DIFFUSION OF THE VAPOR. 



The vapor diffuses rapidly in the open air, as is evident from the 

 spread of the odor. As has been stated, it must be confined closely 

 in order that a sufficient proportion of it may be maintained in the 

 atmosphere to kill insects, which require far less air, even in propor- 

 tion to their size, than do higher forms of animals. The vapor nat- 

 urally tends to spread outward and downward, since it is heavier 

 than air. Consequently when carbon disulphid is applied to a bin 

 of grain or similar material it has been found th.at the killing pro- 

 ceeds outward and downward from the point of application of the 



