Common Signs of a Natural Gas Leak


Natural gas is an important energy source used in homes across the country. It provides fuel for appliances like stoves, ovens, water heaters, and furnaces. While natural gas is generally safe when used properly, gas leaks can occur, putting homeowners at risk. Knowing the signs of a natural gas leak is critical for detecting issues early and preventing serious hazards like explosions and fires. This article will provide extensive information on the common indicators that may signal a natural gas leak in your home. We will explore the specific sights, smells, and sounds that should prompt immediate action to keep your family safe.

Strange Odors

One of the most telltale signs of a gas leak is a strange or unpleasant odor inside the home. Natural gas is intentionally engineered to have a potent, pungent smell that makes leaks easily detectable. Here are some of the most common odor descriptions for escaping gas:

  • Rotten eggs – Since natural gas is odorized with a sulfur compound called mercaptan, leaks often produce a foul rotten egg smell. This is one of the most well-known red flags that gas may be escaping somewhere. If you notice the smell of rotten eggs, it should not be ignored.
  • Skunky – Natural gas leaking indoors can also smell skunky. This strong, unpleasant odor is another surefire sign that gas could be accumulating within the home.
  • Sewage – Gas leaks are sometimes described as smelling like sewage or garbage. This foul stench is an urgent warning that there may be a dangerous leak.
  • Moldy or musty – Some people notice a damp, moldy, or musty odor from gas leaks. This smell should not be confused with common household mildew or mold and should be checked out right away.
  • Hydrocarbons – You may notice an odor like gasoline, oil, or another petroleum product. This scent likely indicates gas escaping somewhere it shouldn’t.

Even a very faintrotten egg or skunk smell could signal a leak, so err on the side of caution if you detect even a whiff of any strange scent. Never ignore a questionable odor inside the home. Gas can quickly overtake a building at high concentrations, so always take action right away if you smell anything odd. Don’t wait to see if the smell gets stronger or dissipates on its own.

Visual Signs

Along with strange scents, escaping natural gas can sometimes generate visible signs within a home. Here are visual cues to watch out for:

Bubbling Water

Active bubbling in standing water around the home is a warning of a possible leak. This includes unusual bubbling in:

  • Toilets or toilet tanks
  • Sinks, tubs, or showers
  • Pet’s water bowls
  • Puddles of water on the floor
  • Outdoor standing water like ponds, pools, or birdbaths

The bubbling action indicates gas escaping from the gas lines or appliances below. The bubbles are created when gas permeates through the water. Don’t dismiss active bubbling, even if you don’t smell gas, as there could be a dangerous accumulation underground. Call the gas company or a plumber to inspect bubbles in standing water right away.

Dirt spraying from the ground

A more dramatic visible sign is dirt, rocks, or debris blowing out from the ground. If you notice spraying or shooting dirt around the property, it likely means a significant volume of gas is breaching underground gas lines and forcing its way up through the soil. This creates an urgent safety issue and risk of fire or explosion. Evacuate the area immediately if you observe dirt or debris spewing up from the ground.

Dead vegetation

Escaping gas can cause vegetation above gas lines to die. If you notice normally green plants turning brown, withering, or dying for no apparent reason, look underground for a potential gas leak. Dead vegetation, especially in one concentrated area, could mark the location of broken gas lines below. Leave the site immediately and call the gas company to inspect for worn or damaged underground piping.

Freezing surfaces

Gas cools as it expands from high pressure lines to low pressure zones. In some cases, a compressed gas leak can chill pipe materials enough for frost or ice to appear. If you see icy spots or frozen areas on metallic surfaces where they shouldn’t be, especially near gas appliances, it may be caused by escaping gas. Report the freezing to the gas company right away for professional assessment.

Unusual Sounds

Natural gas leaks can also produce distinctive sounds signalling a problem. Here are some to listen out for:

  • Hissing – Escaping pressurized gas often causes a hissing noise. If you hear hissing coming from an appliance or gas line, there may be a hazardous leak. The volume of the hiss indicates the size of the leak. Loud hissing signals a major leak requiring quick action.
  • High-pitched squeal – Damaged appliances or fast-moving gas may emit a high-pitched whistling or squealing sound. Never ignore this warning sound.
  • Roaring – Powerful gas flow through cracked pipes or loose fittings can produce a roaring noise like a blowtorch. This deafening sound means there is a dangerous amount of gas escaping.
  • Unusual humming – Appliances like water heaters or stoves may hum or vibrate more loudly than usual if gas is leaking through them. Take note if appliances that normally run quiet start to hum or buzz unexpectedly.

Any strange or inexplicable sounds coming from gas equipment or lines should be checked without delay for potential leakage. Trust your ears, and call for a professional inspection if anything sounds peculiar or excessively loud. It’s better to err on the side of safety.

Additional Clues

Aside from obvious sights, smells, and sounds, be on the lookout for these other subtle signs of a possible gas leak:

  • Unexplained flames or fires – Damaging fires sparked for unknown reasons could stem from a gas leak somewhere on the property. Fires that start without obvious cause may be triggered by escaping gas that pooled somewhere and ignited.
  • Black residue on surfaces – Gas byproducts can leave a sticky black buildup on surfaces near the leak zone. Look for black smears on tile, cement, metals, and other materials. This grimy residue flags a spot where gas may be lingering.
  • Frequent headaches – Headaches from an unknown cause could be a sign of gas exposure. Inhaling even low levels of natural gas can induce frequent headaches. Pay attention to reoccurring head pain, especially if it subsides after you leave the house.
  • Dizziness – Gas inhalation causes a lightheaded, dizzy feeling reminiscent of intoxication. Unexplained wooziness in the home may imply you are being exposed to trace levels of gas. Dizziness should prompt further checks for leaks.

Stay observant for less obvious clues like these that often accompany gas leaks. Never dismiss subtle signs as they could be signaling silent dangers.

Places Where Leaks Occur

Accidental gas leaks can develop almost anywhere that natural gas lines and appliances exist. However, there are some specific spots around the typical home where leaks tend to occur more frequently:

Gas Appliances

Devices fueled by natural gas represent a major potential source of leaks:

  • Water heaters
  • Furnaces
  • Fireplaces
  • Stoves and ovens
  • Clothes dryers
  • Space heaters
  • Pool heaters
  • Gas fire pits
  • Grills

Common problem areas include worn seals and gaskets on appliance doors and lids, loose internal fittings, and cracks or fatigue in the equipment. Homeowners should periodically inspect all gas appliances for potential leakage points. Look for rust, damage, or loose fittings that need repair. Modern appliances have improved safety features, but leaks can still develop over time from use and wear. Replace very old or defective appliances that show signs of deterioration.

Gas Lines and Meters

The miles of buried gas pipelines running to neighborhoods, and the distribution lines branching to individual structures, face constant stresses that can cause cracks and breaks. Gas meter assemblies also contain many threaded fittings and valves that loosen over time. Watch for leaks near:

  • Main gas shutoff valve
  • Pressure regulators
  • Pipe joints
  • Fittings and couplings
  • Valves
  • Gas meter bar and fittings

Outdoor gas lines are especially prone to leakage from weathering, ground movement, corrosion, accidental digging, and other unfavorable conditions. A leak can allow gas to saturate surrounding soil and seep toward buildings.

Unused Chimneys or Vents

Another concealed danger zone is old chimney flues and vents that are no longer in service. Capped-off chimneys create void spaces that can fill with leaking gas. The gas escapes detection and allows dangerous buildup inside chimneys. Make sure all unused chimneys are formally disconnected from the gas supply lines. Install chimney balloons to prevent gas intrusion. Avoid capping vents that may see future use.

Near Appliance Exhaust/Vent Hoods

Leaking gas tends to rise and become trapped near ceilings and upper walls. Areas around kitchen stove vents and bathroom exhaust fans can collect pooling gas. Leaks from malfunctioning appliances commonly spread to their overhead vents. Check the ductwork, filters, and hoods above stoves, dryers, furnaces and water heaters for escaping gas too.

Basements and Crawlspaces

The numerous gas pipes and appliances found in basements make them vulnerable locations for leaks. Gas is also naturally prone to sink into low areas like basements and collect there. Routinely sniff test the basement air for odors and scan all appliances, pipes, and meters for issues. Crawlspaces should be checked too, as leaking gas can seep downward from the floor above.


Attached garages contain gas appliances and piping that can develop leaks. They are also at risk for leaks spreading from the adjacent home. The common garage door threshold gap allows vapors to migrate between house and garage. Be diligent about monitoring garage air quality along with living areas to catch leaks originating next door.

Near Recent Construction or Digging

Any digging or excavation around gas lines creates risk of accidental pipe damage. Heavy construction near a home can also shift and stress buried gas pipes. Pay special attention for possible leaks if trenching, replacement of buried lines, or foundation work has happened nearby. Look for dead vegetation or dirt spraying from the ground. Cruise the perimeter of the property listening for hissing. Be extra vigilant after any neighborhood construction, and call the gas company if anything seems amiss. They will check the buried gas lines with sophisticated gas detectors.

What to Do if You Suspect a Gas Leak

Natural gas emergencies require fast yet careful action. Here are the standard response steps when a leak is suspected:

Evacuate the Area

Leave the structure immediately and get everyone to safety if you smell gas or notice other warning signs. Avoid using any phones, appliances, garage door openers, or other electrical devices on your way out, as sparks could ignite the gas.

Gather pets and head upwind of the gas source to avoid inhaling fumes. Get neighbors to evacuate too if their buildings are at risk. Try to locate where the gas is emanating from as you exit, but don’t linger trying to investigate. Prevent anyone from entering, and keep them away from any bubbling lawns or spewing dirt that could mark a leak epicenter.

Call the Gas Company

Emergency responders need to be contacted promptly once clear of the danger zone. Call the gas company and fire department non-emergency number from outside the home or from a neighbor’s house. Explain the situation and whereabouts of the suspected leak.

Let the gas company professionals inspect with gas detectors and handle shutting off the gas supply lines if needed. Avoid attempting to shut off valves or accessing potentially contaminated areas yourself unless directed by emergency personnel.

Allow Access for Repairs

Stick around the property to provide access and assist crews making necessary repairs and leak checks. Follow all instructions from the responders. Before leaving, get clear direction on when it is safe to re-enter the home and use gas appliances again.

Never restart gas appliances or turn fuel supply valves back on until you receive official word that the system is intact. A dangerous leak could recur if damaged gas pipes or appliances aren’t addressed before gas flow resumes.

Call a Plumber for Appliance Issues

If a faulty appliance like a water heater or stove is to blame, you’ll need follow-up work by a qualified plumber beyond the initial gas shut-off. Have them thoroughly inspect, repair, or replace the problematic unit before using it again. Don’t take chances on older, defective appliances that have already sprung leaks. It may be time to replace them with newer, safer models.

Install Gas Detectors

As a precaution after any leak, add natural gas detectors in the home. Combination smoke and gas alarms are an inexpensive investment that provides an extra measure of warning in case of recurring issues. Installing a combustible gas sensor that directly monitors the furnace fuel line is another wise safeguard. These warning devices can alert homeowners to leaks early before they pose a safety hazard.


How can I check my home appliances for leaks?

Do a sniff test around all appliances and their vents. Use soapy water to check for leaks on valves, fittings, gaskets, and tubing. Look for rust, damage, or loose fittings requiring repair. Signs of soot or heat damage point to leaks. Have appliances periodically inspected by a professional. Replace very old appliances prone to fatigue failures.

What causes natural gas leaks in homes?

Leaks typically happen due to failed or loose fittings on pipes, valves, appliances, and meters. Cracked pipes or hoses also lead to leaks. Appliance seals and gaskets wear out over time. Digging/construction mishaps can damage buried gas lines. Corrosion and material breakdown can produce small perforations. Lower gas line pressure increases leaks.

Can you see a natural gas leak?

Gas is normally invisible, but leaks can sometimes create visible signs like bubbling water, dead vegetation in a line, blowing dirt, vapor clouds, frost on pipes, and black residue deposits near small leaks. Heavy gas accumulation may cause warped air that distorts images above the plume.

Do gas stoves emit gas even when not in use?

A properly operating gas stove will not leak when burners are off. However, a defective stove with loose valves or bad gaskets might allow a slight gas escape. This would generate a faint gas smell near the appliance. Have a professional service the stove if any odor or evidence of leakage appears.

Can a small gas leak be dangerous?

Yes, even a small slow gas leak poses a hazard. Gas inevitably accumulates over time in enclosed spaces with poor ventilation. The gas then becomes a poisoning/asphyxiation risk and potential fire/explosion threat. Since gas leaks tend to worsen, a minor leak today could become a major leak tomorrow. All leaks require prompt response and repair.

How can you detect a gas leak without a detector?

Trust your nose first. Natural gas has an obvious rotten egg or skunk odor at just 5% of its lower explosive limit. Use soapy water to check appliances and pipes for tiny bubbles indicating escaping gas. Notice odd symptoms like headaches or dizziness. Watch for physical signs like dead plants or blowing dirt. Listen for hissing or other strange sounds.

What gases are used to odorize natural gas?

Utility providers mainly use a sulfur compound called mercaptan to create the distinctive rotten egg smell. Some use blends of mercaptans, while another option is ethanethiol which has a decaying cabbage odor. These additives allow gas leaks to be more easily detected by homeowners. The stench warns people of accumulating gas long before it reaches dangerous levels.

Can you light a candle to check for a gas leak?

No, never use an open flame to check for a gas leak. This would be extremely dangerous. The smallest spark can ignite a gas plume. Use your nose to sniff for gas odor, and ventilate the area. Confirm leaks with bubble tests on pipes. Gas detectors also safely check for leaks without open flames.

What can ignite a natural gas leak?

Any flame or spark can ignite a concentrated buildup of gas. Major causes of ignition include burning cigarettes, flames from fires and candles, electric arcs from switches and motors, sparks from metal-metal contact, and static electricity discharge. Gas appliances can ignite leaking fuel if activated. Even buildup of static charge from walking across a carpet can provide enough energy.

What does natural gas smell like when it’s not odorized?

Pure natural gas is colorless and odorless in its natural state. Most gas utilized in buildings is artificially odorized at distribution plants before delivery to your home’s gas lines. This alteration makes leaks detectable. If you ever encounter an unodorized gas leak, it may be evident only by symptoms like wooziness, visual signs, or unusual sounds.


Natural gas powerfully fuels many modern appliances and provides comfortable heat for indoor spaces. But despite advanced safety and warning features, gas leaks continue to occur in structures across the country. Being attentive to the common signs – strange smells, bubbling water, dead plants, odd sounds – provides the best protection by allowing homeowners to catch leaks early. Never hesitate to call the gas company at the first hint of trouble. Take action before small problems mushroom into dangerous leaks. Staying vigilant will keep your family safe and help avoid catastrophic fires and explosions. With knowledge and quick response, natural gas can remain a safe and reliable fuel source for your household needs.