INDUSTRIAL FUMIGATION AGAINST INSECTS 



19 



sary, and compression couplings can be used, except at the main inlet, 

 where the cylinders are connected. 



In large buildings, where there are several floors and numerous 

 branch lines must be used, each floor should be provided with a 

 separate riser, which should be of larger tubing. A spray nozzle 

 (fig. 21) should be provided for at least every 25,000 cubic feet of 

 space, but there should be not more than 10 spray nozzles to a riser. 



Most buildings can be piped with copper tubing at a cost of about 

 10 or 12 cents per 1,000 cubic feet of space. Brass tubing costs about 

 two and one-half times as much as copper. 



The piping system should be so arranged that the gas pressure 

 will be approximately the same at all nozzles, thus insuring an even 

 distribution. Each 

 riser is connected to 

 a special inlet pipe 

 leading through the 

 outside wall of the 

 building to the cylin- 

 ders of gas. 



Applying the Gas 



Each cylinder of 

 liquid hydrocyanic 

 acid is supplied with 

 an inlet valve and an 

 outlet valve. The 

 outlet valve is at- 

 tached to a steel tube 

 connected with the 

 bottom of the cylin- 

 der. The inlet valve 

 leads directly into 

 the top of the cylin- 

 der, 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 been connected with 

 the inlet pipe to the building, is then opened and the gas 

 is forced in. The pressure must be maintained 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 approximately 7 minutes. 



Figure 20. — Installation of three-eighths inch copper pip- 

 ing for introduction of liquid hydrocyanic acid. This 

 piping, being flexible and easily cut with a saw, as in- 

 dicated, can be run along side walls and out along 

 rafters, or to any point where it seems best to install 

 the spray nozzles. 



Safety Precautions 



At the conclusion of the fumigation and after the building has 

 been well ventilated, the spra}^ nozzles should be removed and cleaned 



