Q558. May average blowdown volumes be used when reporting the blowdown vent stacks emission source?

A558. No; the volume involved when determining emissions from blowdown vent stacks by equipment or event type is the unique physical volume of the equipment, vessel, piping, etc. that is blown down, not the gas volume emitted by the blowdown. Reporters must follow methods provided in 40 CFR 98.233(i) of the rule for determining each unique physical volume.