Fishing – trapping – and vermin destroying – Vermin destroying – Fumigators
Patent
1996-01-25
1997-10-21
Rowan, Kurt
Fishing, trapping, and vermin destroying
Vermin destroying
Fumigators
43124, A01M 1300
Patent
active
056783523
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates generally to commodity fumigation processes utilizing substantially reduced concentrations of toxic agent so as to be less hazardous during application and result in substantially less hazardous quantities of residue at the completion of the process, and more particularly, to the use of carbon dioxide as an agent to carry, disperse and increase the effect of a toxic agent such as methyl bromide to be used to eradicate pests located in the commodity or other substance to be fumigated.
BACKGROUND ART
Conventional commodity fumigation processes have required high concentrations of a toxic agent such as methyl bromide in order to achieve effective levels of eradication of a target pest infesting the bulk-stored commodity. If the toxic agent is methyl bromide, the present practice of using at least three pounds of the agent per one thousand cubic feet of commodity volume in order to achieve an effective concentration of the methyl bromide in the commodity. However, by reason of currently effective United States statutes and treaties, the quantity of methyl bromide used in fumigants to be applied to commodities must be reduced by one-half by the year 2000. For applications such as the fumigation of commodities, such as grains, for example, there is presently no equally effective substitute for methyl bromide in use. The conventional fumigation processes for commodities by the use of methyl bromide do not provide for satisfactory kill rates for the target pests at the reduced methyl bromide concentrations to be required for environmental reasons.
In this respect, tests have found that use of methyl bromide at such conventional concentrations in commodities has the potential to result in toxic residues which remain at a dangerous level after the process is completed. This level of residual toxic agent constitutes an unacceptable risk to workers handling the fumigated commodity after the process has been completed.
Toxic agents other than methyl bromide have been used in commodity fumigation processes. The levels of certain other toxic agents required to achieve the similar toxicity effects also result in currently unacceptable levels of toxic residue, requiring long aeration times after the process has been completed.
Typical attempts to solve the problem of residual toxicity in commodities have attempted to use carbon dioxide to control insects in stored grain. This method, set forth in U.S. Department of Agriculture bulletin AAT-S-13/April 1980, requires a carbon dioxide concentration of about 60% to achieve 95% control of most stored grain insects after a four day exposure at temperatures of twenty-seven degrees Celsius or higher. An alternate method of using a low oxygen-nitrogen atmosphere must be held for ten or more days.
U.S. Pat. No. 4,989,363 discloses a process for protecting stored commodities in substantially a gas-filled enclosure of a pesticidal atmosphere comprising 6-100% carbon dioxide.
U.S. Pat. Nos. 4,651,263 and 4,756,117 have attempted to solve the problem. They teach that bulk commodities such as grain infested by pests may be fumigated with phosphine gas. However, at low concentrations, the gas must be maintained three to four weeks. The time may be shortened if the atmosphere is enriched with up to 30% carbon dioxide. The temperature of this process is critical as phosphine gas is explosive. Therefore, raising the temperature of the fumigant gas to decrease the concentration of the fumigant gas by weight cannot be used safely in that process.
Thus there has long been a need for a commodity fumigation process which may utilize toxic agents at lower levels of concentration than presently used in the art while providing a completed fumigation process in a shorter time than has been possible heretofore.
It is desired that at the end of this process the residual levels of toxic agent be significantly reduced to lower, safer toxic limits so that the commodity treated may be aerated and available for use earlier than heretofore practical without unaccept
REFERENCES:
patent: 1861736 (1932-06-01), Bersie
patent: 5063706 (1991-11-01), Aki et al.
Leitner Kenneth D.
Terry Arthur W. R.
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