Cryogenic enclosures can create potential process safety hazards. This publication identifies general hazards and provides guidance to reduce their frequency and consequences. It provides safety guidance and addresses design and operating practices only as they affect safety.

This publication addresses both cryogenic air separation unit (ASU) and hydrogen/carbon monoxide (HYCO) processes. A number of existing publications cover special requirements of these processes and their equipment.

This publication is primarily to document current practices and is intended to apply to new facilities. It is recognized that some existing plants may not meet all recommendations or requirements from this publication. This publication is not intended to be applied retroactively, including where this publication uses the word “shall.”

This publication does not cover the following:

• generally accepted engineering practices for structures and process equipment. Only those issues that are specific to cryogenic enclosures are included;
• enclosures for processes producing liquid hydrogen or helium. The extreme cold temperatures of these processes require specialized knowledge and practices that are beyond the scope of this publication; and
• external structures on/attached to the cryogenic enclosure for example, platforms, ladders, vents, lightning arrestors, etc. For more information on the safe location of oxygen and nitrogen vents relative to the location of platforms and ladders, see CGA P-8.7, Safe Location of Oxygen and Inert Gas Vents.