NSPS Clarification: Venting of Pressure Vessels

Venting of Emissions from Pressure Vessels:
Clarification of 40 CFR 60 Subpart KbA facility has a pressure vessel that meets the exemption requirements of 40 CFR 60.110b(d)(2), except that every seven to ten days, it vents to a 98% efficient control device for a short time. A company asked for an exemption from 40 CFR Part 60 Subpart Kb on the grounds that the pressure vessel did not emit directly to the atmosphere. The exemption provision mentioned above specifies the pressure vessel should operate "without emissions to the atmosphere." It does not matter if emissions are vented directly to the atmosphere or through a control device (with a percentage of the emissions removed). The pressure vessel will vent to atmosphere via the control device, so it is not exempt from the requirements of Kb. Please note that this pressure vessel already exceeds the requirements of 95% control specified under 40 CFR 60.112b(a)(3).