Q557. For blowdown vent stacks does the 98.233.i reference to containers less than 50 cubic feet total physical volume refer to a gas volume or a physical container volume?

A557. The unique physical volume between isolation valves should be considered against the 50 cubic feet threshold for blowdown vent stacks.  As stated in 40 CRF § 98.233(i)(2), unique physical volumes smaller than 50 cubic feet are exempt from reporting under § 98.233(i).  Please see EPA-HQ-OAR-2009-0923-1018-27 in Response to Comments (pages 1464-1465) (http://www.epa.gov/ghgreporting/documents/pdf/2010/Subpart-W_RTC_part2.pdf).