40 CFR §63.1016

1. (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.
2. (b)Recordkeeping. Owners and operators choosing to comply with the requirements of this section shall maintain the records specified in paragraphs (b)(1) through (b)(3) of this section.
   1. (1)Identification of the process unit(s) or affected facilities and the regulated materials they handle.
   2. (2)A schematic of the process unit or affected facility, enclosure, and closed vent system.
   3. (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.