20 



CIRCULAR 869, U. S. DEPT. OF AGRICULTURE 



leads directly into the top of the cylinder, and through it air is 

 pumped, by means of a small compressor (figs. 18 and 19), until a 

 pressure of about 100 pounds is obtained. The outlet valve, which 

 has previously beeen connected with the inlet pipe to the building, 

 is then opened and the gas is forced in. The pressure must be main- 

 tained until the liquid is blown through the pipes into the space to 



be fumigated. As soon 

 as the required quantity 

 of liquid hydrocyanic 

 acid has been forced into 

 the building, the pipe 

 lines are blown clear and 

 the inlet tubes capped. 

 The time needed to pump 

 the contents of a 75- 

 pound cylinder into a 

 building is approxi- 

 mately 7 minutes. 



Safety Precautions 



At the conclusion of 

 the fumigation and after 

 the building has been 

 well ventilated, the spray 

 nozzles should be re- 

 moved and cleaned for 

 storage and the pipes 

 capped. In removing 

 these nozzles, care must 

 be taken to avoid acci- 

 dents from the small 

 quantities of liquid hy- 

 drocyanic acid that some- 

 times remain in the pipes 

 after a fumigation. The 

 operator should never 

 stand directly in front 

 of or beneath a spray 

 nozzle that is being re- 

 moved. 



It is best to use a gas 

 mask in this work. The 

 presence of liquid hydro- 

 cyanic acid behind a noz- 

 zle that is being unscrewed is usually revealed by a well-defined cool- 

 ing sensation and sometimes by a slight odor. Special pressure noz- 

 zles are now on the market which close automatically when the pres- 

 sure 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 thor- 



Figuke 21. — Various attachments lor spray nozzles 

 used in fumigating a wn rehouse, mill, or factory 

 with liquid hydrocyanic acid. 



