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"Standard Atmospheric Condition" for RG 1.194 Instantaneous Puff Release Model

Please provide clarification on the following with regards to the modeling of an instantaneous puff release as described in Section 5 of Regulatory Guide 1.194. The calculation of an effective X/Q for an instantaneous puff release requires that one determine the initial puff volume which has been expanded to standard atmospheric conditions. What is the definition of standard atmospheric condition that one should use, i.e., is it 14.7 psia at 32 degrees F, 68 degrees F, or 212 degrees F?

The agency has not defined standard atmospheric conditions. Standard temperature and pressure is normally defined as air at 0 degrees C (32 degrees F) and 1 atm (14.7 psia), but a temperature closer to 0 degrees C may lead to much larger buoyancy and possibly less conservative results. The American Meteorological Society’s Glossary of Meteorology defines standard atmosphere as air at 15 degrees C (59 degrees F) and 101.320 kPa (14.7 psia). Using a “site-specific” value based on location is an acceptable approach as the standard atmosphere in South Africa is likely much different than that of Florida, New York, or Arizona. Each location could have different “standard” values for their site.