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Gas \u00b7 United States

Gas Piping Symbols — US (IFGC / NFPA 54)

US gas installations follow the International Fuel Gas Code (IFGC) and NFPA 54 (National Fuel Gas Code). These symbols appear on gas piping diagrams, inspection reports, and permit plans. They are used by licensed gasfitters and mechanical contractors across the United States.

IFGC / NFPA 54 / ANSI Z223.115 symbols

Pipework

Low Pressure Gas Pipe

Low pressure gas supply pipe (below 75 mbar)

BS 1553-1

Medium Pressure Gas Pipe

Medium pressure gas pipe (75 mbar to 2 bar)

BS 1553-1

Concealed Gas Pipe

Gas pipe run concealed within the building structure

BS 1553-1

Tee Piece

Gas pipe tee junction

BS 1553-1

Test Point

Gas pressure test point nipple

BS 6891 / Gas Safe

Meters & Controls

Gas Meter

Gas supply meter position

BS 1553-1

Gas Shut-Off Valve

Emergency gas shut-off valve at meter

BS 1553-1 / Gas Safe

Isolating Valve

Manual gas isolation valve for individual appliance

BS 1553-1

Pressure Regulator

Gas pressure regulator / governor

BS 1553-1

Appliances

Gas Furnace / Boiler

Gas-fired furnace or boiler unit

BS 1553-1 / Gas Safe

Gas Fireplace / Space Heater

Gas-fired fireplace or space heating appliance

BS 1553-1

Gas Cooktop / Range

Gas cooking range or cooktop

BS 1553-1

Gas Oven

Gas-fired oven / range cooker

BS 1553-1

Ventilation & Flues

Vent Terminal

Gas vent or chimney terminal (Category I-IV venting)

BS 5440 / Gas Safe

Air Vent

Fixed ventilation opening for combustion air supply

BS 5440-2 / Gas Safe

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Frequently asked questions about gas symbols

What codes govern gas piping symbols in the US?
The International Fuel Gas Code (IFGC) and NFPA 54 (National Fuel Gas Code / ANSI Z223.1) are the primary standards. Most jurisdictions adopt one of these, sometimes with local amendments.
Are gas symbols standardised across all US states?
The symbols are largely consistent as they follow ANSI/ASME standards for piping diagrams. Local jurisdictions may have additional labelling requirements on permit drawings.
What is the difference between Categories I-IV venting?
Venting categories define the flue gas pressure and condensing behaviour. Category I (negative pressure, non-condensing) is most common for standard furnaces. Category IV (positive pressure, condensing) is used for high-efficiency condensing appliances.

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