14 



BULLETIN 872, U. S. DEPARTMENT OF AGRICULTURE. 



and cracks about window frames can be made tight by pasting strips 

 of paper over them. Even an occasional open window and doorways, 

 stairways, and elevator shafts can be fairly well sealed by the use 

 of heavy paper applied in several thicknesses by paper hangers. All 



g r3 



such openings must be closed before fumigation is attempted or fail- 

 ure will result. As the gas has a tendency to rise, each floor should be 

 treated as a unit by closing such openings as those formed by ele- 

 vator shafts, stairways, etc. The small openings through which 



