INDUSTRIAL FUMIGATION AGAINST INSECTS 



21 



storage and the pipes capped. In removing these nozzles, care must 

 be taken to avoid accidents from the small quantities of liquid hy- 

 drocyanic acid that sometimes remain in the pipes after a fumigation. 

 The operator should never stand directly in front of or beneath a 

 spray nozzle that is being removed. 



It is best to use a gas mask in this work. The presence of liquid 

 hydrocyanic acid behind a nozzle that is being unscrewed is usually 

 revealed by a well-defined cooling sensation and sometimes by a slight 

 odor. Special pressure nozzles are now on the market which close 



Figure 19. — Lobby of apartment bouse being fumigated witb hydrocyanic acid 

 gas generated by the discoid method, showing round white wafers distributed 

 over the paper runner and the empty cans from which they have been shaken. 

 These wafers are wet when distributed, but after the evolution of the gas 

 they become dry and harmless. 



automatically when the pressure is removed; hence they do not clog 

 and need not be removed. 



In fumigating with liquid hydrocyanic acid, there is always some 

 danger that the rubber connecting hose may burst under the pressure, 

 showering the operator with the deadly fluid. It is therefore a wise 

 precaution to check the rubber hose and all connections thoroughly 

 before turning on the gas and to wear a gas mask while manipulating 

 the valves of the cylinder. 



THE DISCOID METHOD 



For the fumigation of warehouses that are divided into sections, of 

 mills containing machinery that cannot be easily opened up, or of 



