The International Fuel Gas Code (IFGC) is the model code that governs how natural gas and propane piping, venting, and appliances are installed inside and around buildings. Published by the International Code Council, it is adopted — sometimes with local amendments — by the jurisdictions that then enforce it through permits and inspections.1International Code Council. Why the International Fuel Gas Code Before you start any gas work, confirm which edition your local building department enforces, because the rules below reflect the 2024 edition and local amendments can tighten or modify them.
The code reaches from the point where gas enters the building through the piping, the appliances it feeds, and the vents and chimneys that carry combustion byproducts back outside. It also covers the combustion air that burners need to run cleanly.1International Code Council. Why the International Fuel Gas Code A few things sit outside it: utility distribution mains in the street are federal pipeline territory, and oxygen-fuel welding equipment follows its own industrial standards.
Approved and Prohibited Piping Materials
The IFGC allows several pipe materials, each with conditions attached.
- Steel, stainless steel, and wrought iron pipe must be at least Schedule 10 and meet ASTM A53, A106, or A312.
- Copper and copper alloy tubing must be Type K or L per ASTM B88 or B280, and it cannot be used if the gas contains more than 0.3 grains of hydrogen sulfide per 100 standard cubic feet, because sulfide corrodes copper.
- Corrugated stainless steel tubing (CSST) must be listed to ANSI LC 1/CSA 6.26 and bonded as described below.
- Aluminum alloy is permitted for interior above-grade installations only. No outdoor or underground use.
- Polyethylene plastic is allowed underground only, and must be marked “Gas” and “ASTM D2513.”
Two materials are flatly prohibited for gas service: cast-iron pipe, and PVC or CPVC plastic.2ICC Digital Codes. IFGC 2024 Chapter 4 Gas Piping Installations Both are common in household plumbing and drain work, and that is exactly why they end up misused on gas lines. Don’t.
Buried metallic gas lines also have to contend with soil corrosion, which is why polyethylene is the usual residential choice for underground service. Polyethylene cannot be run inside a building or under a slab, however, so most homes end up with a plastic underground run that transitions to metal where it emerges from the ground.
CSST Bonding for Lightning Protection
CSST is popular for residential remodels because it snakes through wall cavities without threaded joints. Its weakness is lightning: a nearby strike can induce current in the thin corrugated wall, burn a pinhole, and release gas. Section 310.2 of the code addresses this with a mandatory bonding requirement.
Standard yellow-jacketed CSST must be bonded to the building’s grounding electrode system with a copper conductor no smaller than 6 AWG. The bonding wire can be no longer than 75 feet, and it attaches to the gas piping downstream of the meter or second-stage regulator, never to the CSST corrugation itself. One bonding point covers the whole system no matter how many branches it feeds.3International Code Council. CodeNotes: Bonding of Corrugated Stainless Steel Tubing Gas Piping Systems
Arc-resistant CSST, which has a black jacket and an “AR” marking, does not need that direct bond, as long as the entire system uses black CSST with no yellow segments and the gas appliances have an equipment grounding conductor. Mix a single length of yellow into the system and the whole run has to be bonded as if it were yellow throughout.3International Code Council. CodeNotes: Bonding of Corrugated Stainless Steel Tubing Gas Piping Systems
Pressure Testing Before Service
No gas enters a new or modified piping system until it has passed a pressure test. The test pressure must be at least 1.5 times the proposed maximum working pressure, with a floor of 3 psi. Systems with less than 10 cubic feet of internal volume — a typical single-family home — must hold the test for at least 10 minutes. Larger systems need at least 30 minutes per 500 cubic feet of pipe volume, with no test exceeding 24 hours.4ICC Digital Codes. IFGC 2024 Chapter 4 Gas Piping Installations
The test medium is air or an inert gas, never the fuel gas itself. Any pressure drop means a leak that has to be found and fixed before retesting. Gauge readings and duration go into the record as part of the approval.
Sediment Traps and Appliance Shutoffs
Two small components matter at every appliance: a sediment trap and a dedicated shutoff valve.
A sediment trap, sometimes called a drip leg, catches dirt, scale, and moisture before they reach the appliance’s gas valve. The code requires one downstream of each appliance shutoff, as close to the appliance inlet as practical. The usual design is a tee with a capped nipple pointing straight down, so debris drops into the dead end rather than into the burner. Ranges, clothes dryers, outdoor grills, and decorative gas fireplaces are exempt.
Each appliance also needs its own shutoff valve in the same room, within 6 feet, sitting upstream of the flexible connector. The valve cannot be concealed behind permanent construction, though valves behind movable equipment like ranges and dryers still count as accessible. For decorative vented appliances and room heaters, the valve may be installed remotely if it is permanently labeled and serves only that one appliance. Manifold valves must be within 50 feet of the appliance served and clearly identified.
Venting and Chimney Rules
Combustion produces carbon monoxide and water vapor, and the venting system is what keeps those out of the living space. The code matches vent type to appliance category: Type B vents for standard Category I gas appliances and draft-hood units, Type L vents for combination gas-and-oil appliances with hotter exhaust, and masonry or factory-built chimneys where structural and lining requirements are met. A chimney must extend at least 3 feet above the roof penetration and at least 2 feet above any part of the building within 10 feet horizontally.
Gas vents larger than 12 inches in diameter, or those located within 8 feet of a vertical wall, must terminate at least 2 feet above the highest roof penetration point and at least 2 feet above any building surface within 10 feet. Smaller vents farther from obstructions follow a height chart keyed to roof pitch.5ICC Digital Codes. IFGC 2024 Chapter 5 Chimneys and Vents
Clearances From Windows, Doors, and Air Intakes
Where a vent lets exhaust out matters as much as how high it rises. For nondirect-vent terminals, the minimum clearance from an openable window or door is 4 feet below or to the side of the opening, or 1 foot above it. Mechanical air supply inlets need 10 feet of horizontal clearance, or 3 feet vertically above the inlet. Gas vents must also terminate at least 3 feet above any forced-air inlet within 10 feet.5ICC Digital Codes. IFGC 2024 Chapter 5 Chimneys and Vents Direct-vent (sealed-combustion) terminals get smaller allowances for low-input units, as little as 6 inches from an openable window for appliances rated at 10,000 BTU/h or less, because they draw combustion air from outside rather than from the room.
Combustion Air Supply
A burner starved for oxygen produces incomplete combustion, elevated carbon monoxide, and unstable flames. Every enclosed space with a fuel-burning appliance has to have an adequate air supply, and the code gives two paths: use the air already in the building, or bring it in from outside.
Indoor Air Method
If the room and the spaces freely connected to it are large enough, no openings to the outdoors are needed. The baseline figure is 50 cubic feet of connected room volume per 1,000 BTU/h of total appliance input. A 100,000 BTU/h furnace needs at least 5,000 cubic feet of connected space.6International Code Council. CodeNotes: Gas Appliance Combustion, Ventilation and Dilution Air Part 2 – Indoor Combustion Air Methods A sealed-off utility closet does not get to count the rest of the house.
Outdoor Air Method
When the room is too tight, air comes from outside through permanent openings. The two-opening setup places one opening within 12 inches of the ceiling and one within 12 inches of the floor. Each opening needs a free area of at least 1 square inch per 4,000 BTU/h of total appliance input through a vertical duct, or 1 square inch per 2,000 BTU/h through a horizontal duct.7International Code Council. CodeNotes: Gas Appliance Combustion, Ventilation and Dilution Air Part 1 – Outdoor Combustion Air Methods The horizontal duct needs twice the area because air moves less efficiently along level runs.
A single-opening method also exists. One permanent opening within 12 inches of the ceiling, sized at 1 square inch per 3,000 BTU/h, can replace the pair when it connects directly to the outdoors or through a duct. That single opening also has to be at least as large as the combined area of all vent connectors in the space.7International Code Council. CodeNotes: Gas Appliance Combustion, Ventilation and Dilution Air Part 1 – Outdoor Combustion Air Methods
Appliance Placement and Garages
Where an appliance sits matters as much as how it’s connected. Every unit must keep the manufacturer’s specified air gap from combustible materials like wood framing, cabinetry, and drywall. Enough space has to remain for a technician to reach controls, shutoff valves, and serviceable components without tearing out permanent construction.
Garages get stricter treatment because flammable vapors can pool at floor level. Any appliance with an ignition source installed in a garage must be elevated so the lowest ignition source — the pilot light or electronic igniter, not the bottom of the cabinet — sits at least 18 inches above the floor. Rooms that open directly into a garage through doorways or other openings count as part of the garage for this rule.8International Code Council. 2021 International Fuel Gas Code – Section 305.3 Elevation of Ignition Source The exception is appliances specifically listed as flammable-vapor-ignition resistant.
Where a vehicle could strike an appliance, physical barriers like steel bollards or concrete curbs are required. A water heater beside a parking space in an attached garage is the classic case: one careless bumper can rupture a connection.
Permits and Inspections
Essentially every jurisdiction that adopts the IFGC requires a permit before any gas piping installation, modification, or appliance replacement involving the gas supply. Skipping the permit risks more than a fine. It can void homeowner’s insurance and create liability exposure if something later goes wrong.
The inspection sequence is predictable. The contractor runs the piping with every joint exposed. The inspector checks materials, sizing, support spacing, and connections against the approved plan, and either witnesses or reviews the pressure test. Nothing gets closed up behind walls or ceilings until the inspector signs off. Deficiencies come back in a written notice; the contractor corrects them and calls for re-inspection. A final inspection with everything connected and operational confirms the system before occupancy.
Fees vary — some jurisdictions charge a flat rate, others scale by number of appliances or outlets. Many jurisdictions also require that gas work be performed by a licensed plumber or gas fitter rather than a general contractor. The five minutes it takes to check your local building department’s licensing rules before hiring is time well spent.
If You Smell Gas
Even a code-compliant system can develop a leak over time. If you smell the rotten-egg odor added to natural gas or propane, leave the building and take everyone with you. Do not flip light switches, unplug appliances, use your phone, or do anything else that could create a spark; electrical arcing in a gas-vapor atmosphere can trigger ignition. Once outside, call 911 or your gas utility’s emergency line from a neighbor’s phone or a safe distance. Do not go back in until a utility technician or the fire department tells you it is safe.