40 CFR § 63.1016 - Alternative means of emission limitation: Enclosed-vented process units.
(a) Use of closed vent system and control device. Process units of affected facilities or portions of process units of affected facilities enclosed in such a manner that all emissions from equipment leaks are routed to a process or fuel gas system or collected and vented through a closed vent system to a control device meeting the requirements of either § 63.1015 or § 63.1002(b) are exempt from the requirements of §§ 63.1006 through 63.1014. The enclosure shall be maintained under a negative pressure at all times while the process unit or affected facility is in operation to ensure that all emissions are routed to a control device.
(1) Identification of the process unit(s) or affected facilities and the regulated materials they handle.
(3) A description of the system used to create a negative pressure in the enclosure to ensure that all emissions are routed to the control device.