ASME B31.2 was the American Society of Mechanical Engineers’ fuel gas piping code, covering the design, installation, and testing of piping that carried natural gas, manufactured gas, and liquefied petroleum gas from the customer’s meter to the appliance. ASME withdrew it in 1988, and its coverage shifted to NFPA 54, which is also designated ANSI Z223.1 and known as the National Fuel Gas Code. If you are working on fuel gas piping today, NFPA 54 (or the International Fuel Gas Code, depending on local adoption) is what applies, not B31.2.
What B31.2 Covered
B31.2 governed fuel gas piping inside and between buildings. Its jurisdiction started at the outlet of the customer’s meter set assembly (or another agreed-upon delivery point) and ran to the first pressure-containing valve upstream of each gas appliance.1American National Standards Institute. ASME B31.2-1968 – Fuel Gas Piping Everything on the customer’s side of the gas meter, in other words.
The code applied to more than just natural gas. It covered manufactured gas, liquefied petroleum gas (LPG) in the gaseous phase, LPG–air mixtures above the upper combustible limit, and blends of those gases.1American National Standards Institute. ASME B31.2-1968 – Fuel Gas Piping Different fuel gases behave differently under pressure and interact differently with pipe materials and joints, so a single code addressing them all simplified the designer’s work.
Why ASME Withdrew B31.2 in 1988
By the late 1980s, B31.2 overlapped substantially with ANSI Z223.1, which had been published independently as the National Fuel Gas Code. Engineers routinely had to reconcile two documents that covered essentially the same piping. Maintaining both created conflicting requirements and added compliance cost without a corresponding safety benefit.
ASME withdrew B31.2 in 1988 and transferred responsibility for consumer-side fuel gas piping to ANSI Z223.1. That consolidation let technical committees focus on a single, regularly updated standard. ASME still makes the withdrawn B31.2 document available as a historical reference, but it carries no regulatory authority. B31.2 is the only section of the B31 pressure piping series that was withdrawn rather than updated.
What Governs Fuel Gas Piping Now
Three documents cover the territory that B31.2 once occupied, divided by where you are in the gas delivery chain.
NFPA 54 / ANSI Z223.1 — From the Meter to the Appliance
NFPA 54, jointly designated as ANSI Z223.1, is the direct successor to B31.2 for consumer-side piping.2National Fire Protection Association. NFPA 54 Code Development It runs from the point of delivery (typically the meter outlet) to the appliance connections, and it addresses design, materials, fabrication, assembly, installation, testing, inspection, purging, operation, and maintenance. It also sets requirements for combustion air and venting.3American Gas Association. National Fuel Gas Code 2024 Edition
NFPA 54 has built-in pressure boundaries. It applies to natural gas systems at 125 psi or less, LP-gas systems at 50 psi or less, and gas–air mixtures within the flammable range at 10 psi or less.4National Fire Protection Association. NFPA 54 National Fuel Gas Code Systems operating above those thresholds fall outside NFPA 54 and typically require engineering under the ASME B31 pressure piping codes or site-specific analysis.
One important caveat: local jurisdictions decide whether to adopt NFPA 54, the International Fuel Gas Code (IFGC), or an amended version of either. Before starting a project, confirm which model code the municipality has adopted. The applicable code should be identified on the project drawings or in the specification manual.
ASME B31.8 — Transmission and Distribution Up to the Meter
ASME B31.8 covers what sits upstream of the meter: gas transmission pipelines, distribution mains, service lines, compressor stations, and metering and regulation stations. Its jurisdiction explicitly ends at the outlet of the customer’s meter set assembly, at which point it refers users to ANSI Z223.1 and NFPA 54.5American Society of Mechanical Engineers. Gas Transmission and Distribution Piping Systems – ASME B31.8-2003 B31.8 also covers offshore gas gathering pipelines and closed-pipe-type gas storage equipment.6ASME. B31.8 – Gas Transmission and Distribution Piping Systems
The handoff is clean. B31.8 governs everything up to the meter outlet, and NFPA 54 governs everything after it. That dividing line is the same point where B31.2 used to begin.
49 CFR Part 192 — Federal Pipeline Safety
On the federal side, 49 CFR Part 192 prescribes minimum safety requirements for pipeline facilities used to transport gas and is administered by the Pipeline and Hazardous Materials Safety Administration (PHMSA).7eCFR. 49 CFR Part 192 – Transportation of Natural and Other Gas Part 192 applies to pipeline operators handling gas gathering, transmission, and distribution. It does not generally reach customer-premise piping, which NFPA 54 covers, but it governs the utility infrastructure feeding those premises. Operators who violate Part 192 face civil penalties from PHMSA.
If You Have Piping Built to B31.2
Fuel gas piping installed under B31.2 before 1988 does not automatically have to come out. OSHA’s Process Safety Management standard, 29 CFR 1910.119, addresses equipment designed to codes that are no longer in general use.8Occupational Safety and Health Administration. RAGAGEP in Process Safety Management Enforcement Employers may maintain legacy equipment under its original design code, provided their practices still qualify as recognized and generally accepted good engineering practices (RAGAGEP).
Any new work, modification, or extension on a legacy system is a different matter. Inspectors evaluate new work against active codes, so additions and alterations need to meet the current edition of NFPA 54 or whichever code the local jurisdiction has adopted. If you are responsible for a facility with piping originally engineered to B31.2, document the original design basis, maintain it under RAGAGEP, and apply current codes to anything new.
Compliance exposure is not just a code question. OSHA can cite employers for serious violations related to workplace gas piping. Local building and fire inspectors can stop a project, deny an occupancy permit, or require a system to be brought up to code before gas service is restored. Insurance carriers review gas piping compliance during underwriting and after incidents, and a system that does not meet the adopted code becomes a significant factor in determining fault after an accident.
Where B31.2 Sat in the ASME B31 Series
The B31 pressure piping series contains several active sections, each written for a specific service. Seeing the series as a whole explains why B31.2 became redundant rather than essential.
- B31.1 (Power Piping): steam, water, oil, gas, and air systems in power generating stations and industrial plants.
- B31.3 (Process Piping): fluid transportation and storage in petroleum refineries, chemical plants, pharmaceutical facilities, and similar process environments.
- B31.4 (Pipeline Transportation Systems for Liquids): liquid hydrocarbon pipelines between production fields, refineries, pump stations, and terminals.
- B31.5 (Refrigeration Piping): refrigerant and coolant piping and heat transfer components.
- B31.8 (Gas Transmission and Distribution): gas pipelines from gathering through transmission and distribution to the customer’s meter.
- B31.9 (Building Services Piping): low-pressure piping for heating, cooling, and general building services.
- B31.12 (Hydrogen Piping and Pipelines): gaseous and liquid hydrogen service piping.
B31.2 once occupied the gap between B31.8, which stopped at the meter, and the appliance connection. NFPA 54 now fills that gap entirely.