Signs of a gas leak in your home

Here's what to watch for, what to do if you suspect a leak, and what to absolutely never do. Written by a licensed Gold Coast gas fitter.

What natural gas (and LPG) actually smells like

Natural gas is odourless on its own. Gas suppliers add a chemical called mercaptan to make it smell, and it smells like rotten eggs or sulphur. Strong, unpleasant, hard to mistake once you know.

LPG (the gas in bottles for BBQs or rural homes) gets the same additive. Same rotten-egg smell.

If you ever walk into a room and think "what's that smell?", and it smells like sulphur, eggs, or something rotten, treat it as gas until proven otherwise. Don't assume it's the rubbish bin or a dead mouse in the wall. Check first.

LPG vs natural gas: the leak behaviour is different

Both gases get the same mercaptan additive so the smell is similar, but how they behave inside a house when they leak is not the same, and that changes where you check and how you ventilate.

• Natural gas (methane) is lighter than air. It rises. A leak in a kitchen cooktop migrates up to the ceiling first, then spreads sideways across the ceiling, then eventually fills the room from the top down. You'll smell it standing up before you smell it crouched on the floor. Ventilate by opening high windows and roof vents if you have them.
• LPG (propane / butane) is heavier than air. It sinks. A leak from a bottle gas BBQ, a cabin LPG cooktop or an acreage hot water unit pools at floor level first, then fills the room from the bottom up. It is the more dangerous of the two in enclosed low-lying spaces: sub-floor cavities, basements, garages, under-stair cupboards, the boot of a car with a cylinder in it. Ventilate by opening doors low to the ground, and never check for an LPG leak with your face down at floor level.

If you're on bottle LPG (most acreage and hinterland homes, plus caravans and BBQs everywhere) and the smell is faint, also check the ground around the bottle cage on the way out, LPG that has escaped outside still pools in low spots and can drift back into the house if there's a downhill path.

AS/NZS 5601: the standard that runs every gas install in Australia

Every gas appliance install, repair and certification in Queensland (and across the rest of the country) is governed by AS/NZS 5601 Gas installations. That's the technical standard our compliance certificates reference. It covers pipe sizing, regulator selection, flue termination clearances, ventilation requirements for enclosed appliances, isolation valve placement, leak-test procedures, and dozens of other technical details that you won't see on the invoice but that determine whether the install is safe.

What this means practically: if someone has done gas work on your house and there's no compliance certificate referencing AS/NZS 5601, the work is not certified to standard. We come across this regularly, owner-builder work, handyman work, "my mate did it" work. The smell-of-gas call sometimes turns out to be a clearance or ventilation defect that's been baked into the install since day one, not a sudden leak. We won't certify someone else's uncertified work, but we'll re-do it to standard and issue the cert.

Carbon monoxide is a different problem, don't confuse the two

This bit catches people out. Carbon monoxide (CO) is not a gas leak. It's what happens when gas that's already lit doesn't burn cleanly: incomplete combustion at a faulty water heater, a blocked flue, a cracked heat exchanger, a poorly ventilated unflued heater running too long in a closed room.

Key differences between a gas leak and a CO problem:

• A gas leak you can smell. Mercaptan additive, rotten eggs, hard to miss.
• Carbon monoxide is completely odourless and invisible. No smell, no colour. You cannot detect it with your senses.
• Gas leak symptoms are dizziness, headache and nausea plus a strong smell.
• CO poisoning symptoms are headaches, nausea, dizziness, confusion and fatigue with no smell at all. Often worse in the morning if the appliance ran overnight, better when you go outside, worse again when you come back in.

If you have unexplained morning headaches and a gas hot water unit, gas heater or wood-burning appliance inside the house, the suspect is CO, not a gas leak. The fix is a service call on the appliance to check combustion air, flue integrity and heat exchanger condition, plus a CO alarm in any room with a fuel-burning appliance. CO alarms are $25-60 at any hardware shop and they live next to a smoke alarm. Worth it.

Other signs of a gas leak

Smell is the main one, but it's not the only one. Look and listen for:

• A hissing sound near gas pipes, the meter, the cooktop, the hot water unit, or any gas appliance.
• Dust blowing or grass dying in a small spot near where your gas line runs underground (often near the meter on the wall, or in a strip across the yard).
• A yellow flame instead of blue on your cooktop or hot water unit, this is incomplete combustion, often from a bad gas/air mix.
• Soot stains above gas appliances.
• Higher than normal gas bills with no change in your usage.
• Physical symptoms, headaches, nausea, dizziness, fatigue when you're inside but better when you're outside.

Any of these on their own is a "get it checked" sign. More than one together is "get out and call a gas fitter today."

What to do if you smell gas, in order

1. Don't switch anything electrical on or off. Don't flick lights. Don't use the phone inside. A spark from a switch is enough to ignite a gas-air mix.
2. Don't smoke or use any open flame. Obvious, but worth saying.
3. Open windows and external doors if you can do it without crossing through where the smell is strongest. Ventilation reduces gas concentration fast.
4. Turn the gas off at the meter. On natural gas, the meter is usually on an external wall of the house. There's a lever or tap that quarter-turns, turn it 90° to OFF.
5. For LPG bottles, turn the valve on the bottle clockwise until it stops.
6. Get everyone outside. Including pets.
7. Call from outside. Ring us on 0472 657 042 any time, or for a very serious leak, call 000.

What never to do

• Never use a lighter or match to "test" for gas. People still do this. It's how houses explode.
• Never try to fix it yourself, even if you think you know where the leak is. Gas work in QLD is licence-only, and for good reason.
• Never ignore it because "it's only a small smell." Small leaks become big leaks.
• Never use ventilation fans, range hoods, or any electrical air-mover, the motor sparks could ignite the mix.

Why DIY gas work is illegal (and what happens if you try)

In Queensland, any work on gas pipework, fittings, or appliances requires a gas work licence. Unlicensed gas work is illegal, your house insurance won't cover anything that goes wrong, and you can be fined heavily by the Department of Energy and Public Works.

More practically: gas work that isn't done right will either leak or fail later in a much worse way. We've seen homes where someone "swapped a cooktop themselves" and the back of the cooktop was venting gas into the cupboard for weeks before anyone noticed.

What we'll do when we arrive

A licensed gas fitter has the tools to track down a leak fast, an electronic gas detector that sniffs out concentrations of methane in parts-per-million, plus pressure-test gear that pinpoints where in the system the loss is happening.

Most gas leaks fall into one of these buckets:

• A loose fitting or worn seal at an appliance connection, quick fix.
• A perished flexible hose on a cooktop or oven, replace it.
• A corroded or damaged copper line in a wall, open up, repair section, pressure-test.
• A failed regulator on an LPG bottle, replace.
• A leak at the meter union, utility provider job, but we can confirm and report.

Every gas repair we do comes with a compliance certificate. That's the bit that keeps your insurance valid and proves the work was done legally.

How to reduce your risk between checks

• Have your gas appliances serviced annually, especially hot water, heaters and cooktops.
• Replace flexible appliance hoses every 5-7 years; they perish.
• Don't paint over gas lines or fittings, you'll mask early signs of corrosion.
• If you've got an LPG bottle, keep it upright, in a ventilated spot, and never inside the house.
• Install a gas detector if you've got an indoor cooktop or unflued gas heater, they're cheap, they live in the ceiling, they save lives.

If you ever smell something off and you can't explain it, ring us. We'd rather come out and find nothing than not get called when something's actually wrong. 0472 657 042, 24 hours.

What Queensland law says about gas work

Gas work in Queensland is licence-only. Only a person holding a current QBCC plumbing licence AND a Queensland gas work authorisation can install, modify, repair or disconnect gas appliances or pipework. There is no DIY path, no handyman exemption, no minor-work category for the homeowner. Every gas job leaves a compliance certificate, including like-for-like swaps.

Why so strict? Gas leaks kill people. Improperly-installed appliances can leak fuel into a house and cause explosion, fire, or carbon monoxide poisoning. Properly-installed appliances are extremely safe. The licensing regime exists because gas work needs trained people.

The consequences of unlicensed gas work on your property include legal liability if injury or death results, voided home insurance for gas-related incidents, and complications at sale of the house where pre-sale inspections identify uncertified work.

Gas leak emergency response on the Gold Coast

• Business hours emergency callout: $220-380 first hour including travel and diagnosis
• After hours / weekend / public holiday: $340-560 first hour
• Typical simple repair (flexi swap, fitting tighten): $80-280 on top
• Moderate repair (regulator replacement): $200-500 on top
• Complex repair (damaged pipe section): $400-900+ on top
• Total typical emergency call: $400-980

We respond inside the hour 24/7 on the Gold Coast for genuine gas leak emergencies. Phone 0472 657 042.

The LPG-specific picture for acreage

Hinterland properties on LPG bottle gas have different considerations:

• LPG is heavier than air and pools in low-lying areas (basement, sub-floor)
• Auto-changeover regulators have 10-15 year service life
• Both bottles empty simultaneously is sometimes a regulator failure, not just empty bottles
• Bottle cage placement matters for delivery access and safety clearance

For more on LPG systems specifically, see our questions page on how LPG bottle gas systems work on Gold Coast acreage.