INDUSTRIAL FUMIGATION AGAINST INSECTS 29 



Methyl bromide is not recommended for the fumigation of food- 

 stuffs that have a high fat content or for milled cereals intended for 

 human consumption, since these products retain quantities of residual 

 bromides that may be harmful. Unless otherwise noted, a common 

 dosage is 1 pound to each 1,000 cubic feet of space. 



Fumigation With Methyl Bromide-Carbon Dioxide Mixtures 



A mixture of methyl bromide and carbon dioxide is available as 

 a fumigant for use in vacuum chambers, atmospheric vaults, and 

 tight storage rooms. It is sold in steel pressure cylinders containing 

 50 pounds. The dosages recommended vary with the commodity to 

 be fumigated, but under ordinary atmospheric conditions the usual 

 dosage is 15 to 20 pounds of the mixture per 1,000 cubic feet for an 

 exposure of 24 hours. The fumigant is discharged into the atmos- 

 pheric fumigation chamber or storage room in the form of a slush or 

 snow, or as a gas. It is more quickly effective if it is first passed 

 through a vaporizer and introduced as a gas, as is the practice in 

 vacuum, fumigation. 



Fumigation With Methyl Formate-Carbon Dioxide Mixtures 



Warehouses and storage rooms that are thoroughly modern in 

 construction can be fumigated with mixtures of methyl formate and 

 carbon dioxide. Ordinarily these mixtures are used only in special 

 fumigation vaults. The value of methyl formate as a fumigant was 

 first established by the experimental work of this Department. 

 Alone, its vapors are explosive and inflammable in the presence of 

 fire in any form; hence, mixtures with carbon dioxide have been 

 developed, the vapors of which are entirely free from the fire and 

 explosion hazard. 



The methyl formate-carbon dioxide mixtures can be obtained in 

 steel pressure cylinders containing a net weight of 5, 8, 25, 50, or 60 

 pounds. When used in connection with vault fumigation, the cylin- 

 der is set on platform scales close to the vault wall, through which 

 the desired dosage is discharged. The method of application is the 

 same as that recommended for the methyl bromide-carbon dioxide 

 mixture. 



The vapors seem to be harmless to food and other commodities 

 thus far treated, and they are only slightly toxic to man as he ordi- 

 narily comes in contact with them in fumigation work. The recom- 

 mended dosage is 28 pounds per 1,000 cubic feet of empty space, with 

 an exposure of from 12 to 24 hours. Several mixtures have been 

 offered to the public, but one containing about 15 percent of the 

 methyl formate seems to be the most effective and safe. This fumi- 

 gating mixture is similar to the ethylene oxide-carbon dioxide mix- 

 ture in the manner in which it is marketed and used. 



VAULT FUMIGATION 



Many establishments have use for a small fumigation vault for the 

 treatment of incoming raw materials, returned goods, outgoing prod- 

 ucts, etc. Such a vault may be constructed of any material that can 

 be made gastight or reasonably so. 



