How does a facility calculate the Screening Threshold Quantity for propane in a mixture?
Mixtures of propane and other release-flammable COI that contain at least 87.5 percent propane, should be treated as “propane,” subject to the 60,000 – pound STQ rather than a flammable mixture subject to the minimum concentration (i.e., mixtures) provisions applicable to other mixtures of release-flammables. A facility need not include propane in tanks of 10,000 – pounds or less when calculating the 60,000 – pound STQ. The minimum concentration (i.e., mixtures) provisions for release-flammable mixtures apply if the mixture contains less than 87.5 percent propane. For additional information see “Clarification to Chemical Facility Anti-Terrorism Standards; Propane” published in the Federal Register March 21, 2008 (73 FR 5051).
