Natural Gas and Propane Safety

Natural gas and propane heat buildings, water, ovens and dryers. Used inside a sound piping system, they are safe. When they escape, they can burn, explode, push out the oxygen in a room, or create carbon monoxide. You do not need to be a gas fitter to run into this. Anyone who works in or around buildings will eventually smell gas, drill near a gas pipe, or stand beside an appliance that is burning badly. What you do in the first minute matters more than anything else you know about gas.

What You Will Be Able to Do

• Explain how natural gas and propane behave differently when they leak
• Recognize the signs of a gas leak, including the ones that have no smell
• Follow the right steps, in the right order, when you suspect a leak
• Recognize carbon monoxide symptoms and respond to them
• Tell which gas tasks are yours and which belong to a qualified gas worker

How Fuel Gas Behaves

Both gases are colorless and have almost no smell in their natural state. Suppliers add an odorant, usually a sulfur compound called a mercaptan, so a leak smells like rotten eggs or skunk.

"Flammable range" means the mix of gas and air that can ignite. Below it, the mix is too thin to burn. Above it, there is too little oxygen. A room that holds a strong smell of gas may sit anywhere in that range, so never assume it is safe because nothing has happened yet.

Propane is stored as a liquid under pressure. One gallon of liquid boils off into roughly 270 gallons of vapor, so a small liquid leak makes a large gas cloud. Because propane sinks, it can pool in a low spot and stay there long after the smell fades upstairs. Liquid propane is also very cold when it escapes and can freeze skin on contact.

Signs of a Leak

Smell is the first warning, but it is not the only one.

• Smell: Rotten eggs, sulfur, or skunk.
• Sound: Hissing or whistling near a pipe, meter, tank, or appliance.
• Sight: Dirt blowing up from the ground, bubbles rising in standing water, or a patch of dead plants above a buried line.
• Your body: Headache, dizziness, or nausea in a space where you smell gas.

Do not rely on your nose alone. Odorant can fade when gas passes through soil or sits in a new steel tank or pipe. Some people have a weak sense of smell, and everyone stops noticing an odor after a few minutes in it. If a gas detector alarms or a coworker smells gas and you do not, treat it as a leak.

What to Do If You Suspect a Leak

Do these in order. Speed matters more than being certain you are right.

1. Stop what you are doing. Do not finish the cut, the weld, or the call.
2. Leave everything off or on as it is. Do not touch light switches, thermostats, appliances, or anything else that could spark. Do not light anything.
3. Get everyone out. Warn the people around you as you go, and leave doors open behind you if you can do it without slowing down.
4. Go well away from the building. Walk upwind. Do not start a vehicle or power equipment near the area.
5. Call from a safe distance. Call 911 or the gas utility's emergency number once you are away from the building. For propane, call 911 or the propane supplier. Do not use a phone inside.
6. Stay out. Keep others out until emergency responders or the utility say it is safe.

Warning: Do not try to find the leak or shut off the gas at the meter or tank yourself unless you are a trained gas worker, or the utility or your site's emergency plan tells you to and you can do it from outside. People have been killed going back in to help.

Once gas has been shut off for a safety reason, only the utility, the supplier, or a qualified gas worker turns it back on. Every pilot and appliance has to be checked when service returns.

Carbon Monoxide

Burning gas needs enough air and a working vent. When either fails, the flame makes carbon monoxide (CO). You cannot see, smell, or taste it, and the odorant in fuel gas does nothing to warn you, because CO is not fuel gas.

Early symptoms feel like the flu: headache, dizziness, nausea, weakness, and confusion. If several people in one place feel sick at once, or people feel better after leaving the building, suspect CO.

Warning signs at an appliance:

• A flame that is yellow, orange, or lazy instead of steady and blue
• Soot or scorch marks around a burner, vent, or draft hood
• Heavy condensation on windows near the appliance
• A vent pipe that is disconnected, rusted through, or blocked
• A CO alarm sounding

If a CO alarm sounds or you suspect CO, get everyone into fresh air and call 911. Do not stay to open windows or look for the source. Anyone with symptoms needs medical care, even if they start to feel better outside. Never run a gas engine, generator, or propane-powered machine in a closed space. The same danger comes from any fuel-burning equipment used without enough ventilation.

Working Near Gas Piping

Most gas accidents on a job come from people who were not doing gas work. Before you cut, drill, dig, or move anything, think about what might be behind or below it.

• Before you dig: Have buried lines marked through the 811 call system, even for a shallow hole. Private lines to a garage, grill, pool heater, or tank are often not marked by the utility, so ask the owner and consider a private locator.
• Before you drill or cut: Look for gas pipe in walls, floors, and ceilings. Yellow or black flexible tubing (corrugated stainless steel tubing, or CSST) is thin-walled and easy to puncture.
• Around pipe and meters: Do not hang anything from gas pipe, use it as a step or a support, or use it as an electrical ground. Keep meters, regulators, and vents clear, and do not bury them under mulch, snow, or stored material.
• Around appliances: Do not pull a range, dryer, or water heater away from the wall until you know how it is connected. A stiff or old connector can crack when moved.
• Around ignition sources: Keep torches, grinders, and sparks away from any line that has been opened. Keep flammable liquids away from pilot lights and burners. Vapors travel along the floor.

If you hit a gas line, even if you see only a scrape on the coating, stop and report it. A small nick can fail later. If gas is escaping, leave the equipment where it is and follow the leak steps above.

Propane Tanks and Cylinders

• Store cylinders outdoors, upright, and away from doors, windows, and air intakes. Do not store them in a basement, living space, or vehicle.
• Keep tanks and regulators clear of anything that could block the relief valve.
• Close the valve when a cylinder is not in use, even when it is empty. An "empty" cylinder still holds vapor.
• Never heat a cylinder or tamper with its relief valve.

What Is and Is Not Yours to Touch

Rules on who can do gas work vary by state and city, and many places require a license. When a rule and this table differ, the local rule wins.

Common Mistakes

Check Your Understanding

1. You are working in a basement and notice a faint rotten-egg smell near a floor drain. The building uses propane. What do you do?

Treat it as a leak. Propane sinks and collects in low places, so a faint smell in a basement is a serious sign. Stop work, touch no switches, get everyone out, and call 911 or the supplier from a safe distance.

2. Two coworkers in a mechanical room have headaches and feel better when they step outside. No one smells gas. What might be happening?

Carbon monoxide. CO has no smell and the gas odorant does not warn you about it. Get everyone into fresh air, call 911, and do not go back in until responders clear the room.

3. Your drill bit touches a yellow flexible tube inside a wall. Nothing seems to be leaking. What now?

Stop and report it. That is likely CSST, which has a thin wall. Even a scrape can fail later, so a qualified gas worker needs to inspect it before the wall is closed.

4. The gas was shut off after a leak, and the repair looks finished. The owner asks you to turn the valve back on. What do you say?

No. Only the utility, the supplier, or a qualified gas worker restores gas, because every appliance and pilot must be checked first.

Key Takeaways

• Natural gas rises and propane sinks, so a leak collects in different places.
• If you suspect a leak, leave first and call from a safe distance. Do not touch switches or try to find the source.
• Smell is a warning sign, not a guarantee. Odor can fade, and your nose can tire.
• Carbon monoxide comes from bad combustion, has no smell, and calls for fresh air and 911.
• Mark buried lines before you dig and check walls before you drill.
• Pipe, connectors, regulators, and meters belong to qualified gas workers and the utility.