INDUSTRIAL FUMIGATION AGAINST INSECTS 11 



on the lower floors, since gas concentrations tend to become equalized 

 in all parts of the building shortly after the fumigant is introduced. 

 The fumigant should be applied from the outside if possible, and 

 the fumigation crew should be supplied with gas masks having 

 canisters designed for protection against the gas to be used. 

 Even when the equipment used in applying the gas is outside the 

 bin or building, leaking connections, broken tubing, and gas 

 leaking from the bin or building are encountered so often that 

 protection is necessary at all times. 



Before the fumigation is started, the building should be 

 thoroughly searched to make sure that no workmen or visitors 

 are inside. During the fumigation all entrances to the building 

 should be kept locked and usually guarded by watchmen. 

 Placards warning people to keep out should always be tacked 

 on all doors. Each operator should be familiar with the entire 

 plan of procedure as well as with his own particular job. The 

 entire operation should be under the supervision of a thoroughly 

 experienced man ready to give assistance in case anyone gets 

 into trouble. Help given at the right time will prevent possible 

 fatal accidents. 



Ventilating the Building After Fumigation 



After the fumigation the building should be aired out by open- 

 ing doors and windows, if possible from the outside. Wherever 

 it is necessary to open certain windows from the inside, all open- 

 ings accessible from the outside should be opened first, and the 

 building aired out as well as possible by that means before men 

 (wearing gas masks) are permitted to enter, for concentrations of 

 gas higher than the capacity of the gas-mask canister are fre- 

 quently encountered under these conditions. The skin of the 

 operators should also be completely protected, since many of the 

 fumigating gases are absorbed through the skin. It is important 

 that watchmen be instructed to prevent anyone from entering 

 the building while it is being ventilated. A large proportion of 

 the fatalities connected with fumigation have been due to criminal 

 neglect on the part of watchmen. 



Fumigation With Hydrocyanic Acid Gas 



For the fumigation of large buildings there is no more efficient gas 

 than hydrocyanic acid. It is relatively inexpensive, kills with great 

 rapidity, and, although deadly poisonous, can be handled with reason- 

 able safety by experienced men. It can be used in nearly all types 

 of buildings and will not injure most articles of commerce. 



Hydrocyanic acid gas is commonly produced in one of four ways: 

 (1) By generating it in a barrel, earthenware crock, or other container 

 from a mixture of sodium cyanide, sulfuric acid, and water — the so- 

 called barrel or pot method ; (2) by pumping it into the building or 

 machinery in liquid form from cylinders — the liquid method; (3) by 

 spreading on the floor of the building an absorbent material saturated 

 with liquid hydrocyanic acid — the discoid method; (4) by spreading 

 on the floor of the building a powder consisting of calcium cyanide, 



