How to Detect Gas Leak and What to Do Immediately

Gas Leak in Your House: How to Detect It & What to Do Immediately

A strange smell you can’t ignore. A faint hissing sound that wasn’t there before. A gas flame that suddenly looks off. When things like this show up at home, it’s not something you can afford to ignore.

In this guide, we’ll walk you through these warning signs so you can quickly assess if it’s a gas leak and what to do immediately to stay safe.

TL;DR

Signs of a gas leak are rotten egg/sulphur smell, hissing or whistling near pipes or appliances, yellow/orange burner flames, dead or discoloured grass patches, sudden dizziness/nausea indoors, unusual ground disturbance or mist, and high gas bills.
When a leak is suspected, avoid any ignition sources, leave the house, move everyone to a safe outdoor area, and call emergency services or a licensed gas fitter.
Only go back in the house after a licensed gas fitter or emergency technician confirms safety using gas detectors and the area has been ventilated and fully checked for remaining risk.
Common causes of gas leaks are worn-out appliance seals, loose pipe joints, corrosion or rust in older pipes, accidental damage during DIY or digging, poor installation work, or faulty burners.
To prevent leaks, have a professional service the appliances every 2 years; install detectors; keep appliances clean and well-ventilated; avoid DIY gas work; protect underground lines before digging; and act early on any unusual signs.

The Most Common Signs of a Gas Leak in a House

A Strange Smell Like Rotten Eggs

If you smell strong odours of rotten eggs near your cooktop, hot water system, heater, or bayonet fitting, that’s the biggest and most immediate sign of a gas leak.

Gas is odourless and invisible, so most leaks go undetected. That is why gas suppliers add a chemical called mercaptan, which has a very strong, unpleasant smell, so even a small leak becomes obvious straight away.

Hissing or Whistling Noises Near Gas Lines

Gas in your pipes is under pressure. When there’s a crack, a loose connection, or a worn seal, the gas gets forced out through that small opening. As it escapes, it creates a steady hissing or light whistling sound, similar to air leaking from a pricked balloon.

You’ll usually hear this near gas appliances, along exposed pipes, or around the metre. It’s often more noticeable in quiet moments, like late at night.

Bubbles in Standing Water

Gas is invisible, but you can still spot a leak if it passes through water.

If you suspect a leak, apply soapy water to a pipe joint or the area you think might be affected; escaping gas will push through the liquid and form bubbles.

The same thing can happen outdoors. If there’s a leak in an underground gas line, you will see bubbles in the puddle, damp ground, or muddy patch above it. That bubbling happens because the gas is rising to the surface and forcing its way through the moisture.

Dead or Discoloured Patches of Grass

When a leak occurs underground, the gas escapes into the soil and replaces the oxygen that plant roots need to survive. Without oxygen, the roots can’t survive, and the grass above starts to weaken and die.

So, if you notice a patch or strip of grass turning yellow or brown while the rest of your lawn looks healthy – especially if that patch follows a straight line where a gas pipe is likely running – it often points to an underground gas leak rather than a watering or soil issue.

A Yellow or Orange Burner Flame

Gas needs oxygen from the air to burn properly and release carbon dioxide (CO₂).

A healthy flame should be blue and steady. That blue colour shows the gas is mixing well with enough oxygen and burning fully. This is called complete combustion, and it’s how your appliance is meant to work.

If the flame turns yellow or orange, it means the gas isn’t getting enough oxygen while burning. This usually happens when the burner holes are partly blocked with dirt, grease, or soot, so less air mixes with the gas.

Because of this, the gas burns incompletely, and instead of producing CO₂, it releases carbon monoxide (CO) (a dangerous, invisible gas) and soot that appears as black or oily marks around the burner or on cookware. Some of the gas may not burn at all and can escape into the surrounding air.

So, while the yellow flame itself is a sign of a faulty appliance and poor burning, the result is a slow buildup of raw gas or dangerous carbon monoxide in your room every time the stove is on.

Physical Symptoms

When gas leaks into a room, it starts to replace the oxygen in the air. Your body needs oxygen to breathe, so even a small drop in its concentration in the air can affect you quickly.

That’s why you might experience:

A sudden, heavy headache
Dizziness or light-headedness
Nausea or a sick feeling
Feeling tired for no clear reason

But how can you tell it’s the air inside, not just a cold or fatigue? You can confirm this through a location test. Step outside into fresh air and see what happens.

If the symptoms start to ease – your headache settles, the dizziness reduces, and you begin to feel normal – that’s a strong sign the indoor air is the issue.
Then, if you go back inside and the symptoms return, it points to a possible gas buildup affecting the air quality in the room.

Unusual Clouds, Mist, or Moving Dust

If a pipe is damaged or ruptures, the gas can escape in a strong, fast stream. That sudden release pushes against the air and tiny particles around it, so you might notice dust, dirt, or dry leaves moving or swirling in one small area, even when there’s no wind.

You might also notice a slightly disturbed or unsettled patch of ground because the gas coming out from below is displacing the air and soil particles at the surface, which can make that spot look different from the rest of the ground.

In some situations, especially in cooler early mornings in places like Townsville, where humidity is higher, you might also see a faint white mist or fog close to the ground. This happens because when gas is released quickly, it expands and cools the surrounding air. That rapid cooling causes moisture already in the air to condense into tiny water droplets, which you see as a visible mist.

A Sudden Spike in Your Gas Bill

If your daily habits haven’t changed (same cooking, same hot water use) but your bill suddenly jumps, it usually means gas is escaping through a leak, or there may be a billing error, which is rare.

You can do a simple metre check at home to find if there is a gas leak.

Turn off all your gas appliances, but leave the main gas supply on. Then go and look at your gas metre, which is found in a metal box at the front or along the side of your house. If the numbers are still moving or the dial is still spinning, it means gas is still flowing through the system, so there is a leak.

Can You Have a Gas Leak Without Smelling It?

Yes, you might not smell a gas leak because of the following reasons:

Odour fade: Even though gas companies mix a smelly chemical (mercaptan) into the gas lines, that smell doesn’t always stay strong. If a leak happens in a pipe buried deep underground or behind a brick wall, the soil and concrete can act like a giant filter. As the gas passes through these materials, the mercaptan gets absorbed, so the gas that eventually seeps into your room is odourless.
Olfactory fatigue: Your body will not sense a smell as dangerous if you are around it for too long. This is called olfactory fatigue. If you have a very slow, tiny leak that has been hissing for days, your brain might start to ignore the scent because it thinks the smell is just a normal part of the house.
Masking and sinus issues: If you’ve been cooking a spicy curry, using strong cleaning products, or have a scented candle burning, these can mask the smell of a gas leak. Also, if you have a cold, hay fever, or a reduced sense of smell, you might be completely nose-blind to the danger.

This is why relying on a scent only is risky. If you don’t smell anything, but you notice other signs we discussed, there is likely a gas leak.

What To Do Immediately If You Suspect a Gas Leak

Stop what you’re doing and freeze: The very first rule is not to touch anything electrical. Don’t flick a light switch, don’t unplug the toaster, and don’t use a torch or a lighter. Even a tiny spark from a switch or appliance can ignite gas in the air and cause a fire.
Evacuate everyone immediately: Get your family and pets out of the house and move to a safe outdoor spot, like the footpath across the road or a neighbour’s driveway.
Open the house up (only if it’s quick and safe): While leaving, if doors or windows are right there, open them on your way out. This helps trapped gas spread into the open air and reduces its concentration inside the house.
Call the professionals: Once you are safely away from the house, call your local gas distributor’s emergency line or 000 if you believe there is immediate danger (strong smell or severe physical symptoms). Emergency teams have equipment to locate and isolate the leak safely.
Turn off the gas at the source (only if it’s safe): If the gas metre or LPG cylinder is outside and easy to reach, turn it off at the valve to stop more gas from entering your home while you wait for help.
- For a natural gas metre, use a wrench or your hand to turn the yellow handle a quarter-turn until it is across the pipe (at a right angle) to stop the flow.
- If you use LPG bottles, turn the handwheel on top of the cylinder clockwise until it is tight.

What NOT To Do During a Suspected Gas Leak

Touch any switches: Do not turn lights on or off, and do not use any appliances. When you flick a switch, it creates a tiny, invisible spark inside the wall, and that spark can ignite the gas in the air instantly.
Use a phone inside: Avoid using your mobile phone, a landline, or even a tablet when inside. Even though you don’t see it, these devices use electrical energy that can cause a spark. Make your calls only once you are safely outside.
Use matches, lighters, or candles: It sounds obvious, but never try to find the leak with a flame. Also, don’t smoke or light a cigarette anywhere near the house. Natural gas and LPG are highly flammable, which means they can catch fire very easily with even a small flame.
Start your car: If your car is parked in a garage or close to the house, leave it there. Starting an engine creates a lot of heat and sparks under the bonnet. If gas has built up in your garage, turning the key could be very dangerous and can lead to a fire.
Try to find the leak yourself: Don’t remove wall panels, inspect pipes, or try to trace where the gas is coming from. Without proper tools, you can make the situation worse or accidentally create a spark.
Re-enter the house: Once you have walked outside, stay there. Do not go back in to grab your charger, your wallet, or your shoes. Gas can collect in different areas of the house where you might not smell it, so it’s safest to wait until professionals confirm it’s clear.
Turn the gas back on: If you managed to switch off the gas at the metre or cylinder, leave it off. Even if the smell disappears, there could still be an active fault. Only turn on the system when a licensed gas fitter says it is safe to do so.

When It Is Safe to Go Back Inside

You can only go back inside your home once a licensed gas fitter or an emergency technician from your local gas distributor has officially confirmed it is safe.

Once the leak is found and fixed, the technician will ventilate the house by opening doors and windows to clear out any remaining gas. They then use detectors to check gas levels in real time. If only they measure a safe reading of 0% LEL (Lower Explosive Limit), which means there is no detectable gas risk, they will let you back in.

How To Help Prevent a Gas Leak in the Future

You can prevent most gas leaks by adopting a few simple habits and catching small issues early before they turn into bigger problems.

Book a check-up for your appliances: Have a licensed gas fitter inspect your gas appliances every 1-2 years. They check seals, valves, and connections for wear and test the system to make sure everything is gas-tight.
Install gas and carbon monoxide detectors: Some gas issues have no smell, especially carbon monoxide (CO), so detectors are an important safety layer. A gas detector picks up leaking natural gas or LPG, while a CO detector alerts you to dangerous carbon monoxide in the air. Place them near gas appliances like heaters and also near bedrooms so you’re alerted early if gas or CO builds up anywhere in the home.
Keep things clean and clear: Gas appliances need proper airflow to burn safely. Avoid placing boxes, clothes, or curtains too close to heaters or hot water units. Also, keep stove burners clean from grease and food build-up. If burners get blocked, gas won’t flow or burn properly, which can lead to incomplete combustion.
Only hire licensed professionals: Don’t try to install or repair gas appliances yourself. In Townsville, only a licensed gas fitter is legally allowed to carry out this work. This ensures connections are secure and reduces the risk of leaks or faults.
Protect your gas pipes: Before digging or doing any outdoor work, check where your gas lines run so you do not hit them. Use services like Before You Dig Australia to locate underground utilities before starting any work.
Watch for warning signs early: Pay attention to small changes in the house. If a blue flame turns yellow or orange, or you see soot building up around an appliance, don’t ignore it. These are early signs that gas isn’t being burned properly. Fixing it early can prevent a more serious leak later.

Final Thoughts

Gas builds up quickly in a closed space and can affect your health, causing headaches, dizziness, nausea, or feelings of confusion. And once it has filled your space, something as small as a switch turning on can be enough to set a fire off.

So if you notice anything like a rotten egg smell, hissing sounds, or dead grass patches in the yard, leave the house immediately and then call for professional help.

From there, a licensed gas fitter or emergency technician will come in, track down the issue, fix it or isolate the faulty part, and then properly test the system to make sure there’s no leak left. You only go back inside once they’ve checked everything and confirmed it’s safe again.

FAQs

Can I stay in my house if I only smell a tiny bit of gas?

No, you should not stay in your house if you smell gas, no matter how small the amount seems. Even a faint smell can mean gas is building up inside the space, and it only takes one spark, like a fridge motor switching on or a light turning on, to ignite it.

The safest step is to leave the house immediately and wait in a safe outdoor spot, like the footpath or across the road, until a licensed gas fitter or emergency service confirms it is safe to go back inside.

Why can I smell gas, but my carbon monoxide alarm isn’t going off?

This is a very common confusion, because people think all gas is the same, but it isn’t.

Your carbon monoxide (CO) alarm, as the name says, only detects carbon monoxide, which is a gas produced when fuel burns incompletely (due to a lack of oxygen) inside appliances.

But the rotten egg smell you notice is unburnt gas (natural gas or LPG) that is leaking from a pipe or connection before it is burned. CO alarms are not designed to detect this.

That’s why we recommend installing both gas and CO detectors in your house.

How much does it usually cost to fix a gas leak in Townsville?

In Townsville, the standard call-out and repair work is around $100 to $280+ per hour. If it’s an emergency or after-hours job, the rate is often higher, typically $300+ per hour, along with a call-out fee that usually falls between $150 and $300.

Smaller issues, like tightening a loose fitting, are quick to fix and cost less. But if the leak involves a damaged pipe or a faulty appliance that needs replacement, the total cost will naturally be higher.

Who do I call for a gas leak in Townsville?

For a gas leak, the first step is always to evacuate the area immediately and move to a safe distance.

Once you’re outside, contact your local gas distributor or emergency service. You can call Origin Energy on 1800 808 526 for both natural gas and LPG-related issues or North Regional Gas on 07 4774 5111 for LPG leaks.

If the situation feels highly dangerous (strong gas smell, visible damage, or any sign of fire), call 000 right away, which is Australia’s main emergency number used for urgent situations involving fire, medical emergencies, or life-threatening danger.

Can a gas leak make my pets sick before I notice it?

Yes. Pets like dogs and cats are often affected earlier because they are smaller and breathe faster than humans.

They may show signs like unusual tiredness, vomiting, confusion, or restlessness. Sometimes they may try to leave the house or avoid certain areas.

If you notice these signs along with even a faint gas smell or other warning signs, move your pets outside immediately and treat it as a possible gas leak situation.