Frequent Questions

Threshold determination for mixture containing flammable substance and water

A stationary source has in a process a mixture containing 9,000 pounds of butane and 1,001 pounds of water.  The mixture meets the criteria for a National Fire Protection Association flammability rating of 4 (NFPA 4).  Is this process covered under the RMP regulations?


Yes. Where the concentration of the regulated flammable substance in the mixture is one percent or more by weight of the mixture, the entire weight of the mixture must be applied toward the 10,000 pound threshold quantity for the flammable substance unless the owner or operator can demonstrate that the mixture itself does not have an NFPA flammability hazard rating of 4 (40 CFR 68.115(b)(2)). Because this mixture does have an NFPA 4 rating and is present in a process in an amount greater than the threshold quantity, the process is a covered process under the risk management program regulations at 40 CFR Part 68.


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