ASHRAE Standard 15 establishes safeguards for life, limb, health, and property and prescribes safety requirements. This standard is directed toward the safety of persons and property on or near the premises where refrigeration facilities are located. It includes specifications for fabrication of tight systems but does not address the effects of refrigerant emissions on the environment. This standard applies to (a) the design, construction, test, installation, operation, and inspection of mechanical and absorption refrigeration systems, including heat pump systems used in stationary applications; (b) modifications including replacement of parts or components if they are not identical in function and capacity; and (c) substitutions of refrigerant having a different designation.
The 2016 edition incorporates Addenda a, b, c, e, g to ASHRAE Standard 15-2013, which comprise the following changes to the 2013 edition:

• Incorporated changes to improve in the safe design, construction,installation, and operation of refrigeration systems.
• Updated requirements for safety relief systems, including revisions to relief vent pipe discharge locations and design provisions for headered relief vent systems
• Updated design pressure requirements applicable to systems using carbon dioxide;
• Modified overpressure protection for heat exchangers and pressure limiting devices for positive displacement compressors.

ASHRAE Standard 34 is intended to establish a simple means of referring to common refrigerants instead of using the chemical name, formula, or trade name. It establishes a uniform system for assigning reference numbers, safety classifications, and refrigerant concentration limits to refrigerants. The standard also identifies requirements to apply for designations and safety classifications for refrigerants and to determine refrigerant concentration limits. This standard provides an unambiguous system for numbering refrigerants and assigning composition-designating prefixes for refrigerants. Safety classifications based on toxicity and flammability data are included along with refrigerant concentration limits for the refrigerants. This standard does not imply endorsement or concurrence that individual refrigerant blends are suitable for any particular application.
The 2016 edition incorporates the 35 approved and published addenda to Standard 34-2013. Among the key changes to the 2016 edition are the following:

• Added thirty new refrigerants.
• Changed the source of the WEEL (Workplace Environmental Exposure Levels) values from AIHA (American Industrial Hygiene Association) to TERA OARS-WEEL (Toxicology Excellence for Risk Assessment/Occupational Alliance for Risk Science).
• Changed requirements for the refrigerant application process.
• Changed the requirement for submission of standard test result data to validate the method used to determine burning velocity.
• Changed units required for refrigerant designation to require the submission of dual units.
• Revised R-744 toxicity data for the RCL, LC 50, cardiac sensitization NOEL, anesthesia NOEL, ATEL, RCL, and ATEL source.