Detect gas leaks by smell, sound, and physical signs, then act fast — no switches, no flames, evacuate immediately, and call emergency services from outside.
Natural gas and LPG (liquefied petroleum gas) are among the most useful and most dangerous utilities in any home. A significant gas leak carries two primary risks: asphyxiation if gas displaces breathable oxygen, and explosion if gas accumulates to a concentration between 5% and 15% in air (the explosive range for natural gas) and encounters an ignition source. That ignition source can be as subtle as a light switch being flipped, a doorbell ringing, or a phone vibrating on a surface.
In 2020, gas explosions and fires caused thousands of injuries and several hundred deaths in the US alone. The vast majority are preventable. Knowing how to detect a leak and what to do — and what never to do — in the first two minutes is the difference between a safe evacuation and a catastrophe.
Understanding sources helps you recognise risks early:
Natural gas is odourless in its pure form. Gas suppliers add mercaptan (methyl mercaptan), which produces a sharp, sulphurous smell often described as rotten eggs or a struck match. This odorant is detectable at concentrations far below the explosive threshold — it is your earliest warning system.
LPG (butane, propane) has a similar smell, sometimes described as slightly sweeter or more like petrol.
⚠️ Do not assume the smell is from cooking or another source and dismiss it. If you smell gas in your home, treat it as a leak until proven otherwise.
A hissing or blowing sound near a gas pipe, appliance, or connection point may indicate escaping gas. This sound is usually quiet — listen carefully, particularly near:
In some cases, particularly with outdoor or underground leaks, you may notice:
A wall-mounted natural gas or LPG detector (separate from a CO detector — they detect different gases) provides the earliest electronic warning. These are particularly valuable in kitchen/boiler areas and should be installed at low level for LPG (which is heavier than air and sinks) and at high level for natural gas (lighter than air, rises).
⚠️ Do not rely solely on smell — some people have a reduced sense of smell, especially after illness or in older age. A detector provides reliable, unambiguous warning.
If you smell gas, hear a hiss, or your detector alarms:
This is the most critical rule. Do not turn lights on or off. Do not press a doorbell. Do not use a landline handset. Do not unplug appliances. Any electrical arc — even the tiny one produced by a light switch — can ignite accumulated gas. This includes:
If a gas burner is lit, turn it off at the appliance. Do not light cigarettes, candles, or matches. If a candle is already burning, blow it out.
If windows and doors are within immediate reach as you move toward the exit, open them. Fresh air can dilute gas concentration. However, do not delay your evacuation to do this — getting out takes priority.
The gas stopcock (isolation valve) at the meter can be turned to cut supply. Turn it 90 degrees so the handle is at right angles to the pipe. Do this only if:
If you are not sure where the meter is, skip this step and evacuate.
Leave the building immediately. Take household members, including pets if they are immediately to hand. Do not stop to collect belongings, turn off appliances, or investigate the source.
Move to a point at least 50 metres from the building before stopping. Do not cluster around the front door — if gas has accumulated and ignites, the blast extends outward. Move to the street or a neighbour's property.
⚠️ Do not re-enter the building under any circumstances until emergency services have cleared it.
Once you are safely outside, call:
Use a mobile phone outside the building — not a landline inside. Emergency responders will arrive to isolate the supply and check whether the building is safe to re-enter.
| Action | Why It Is Dangerous |
|---|---|
| Flip a light switch | Electrical arc can ignite gas |
| Use a landline phone indoors | Can spark ignition |
| Start a car in an attached garage | Engine ignition; exhaust spark |
| Try to find the leak source | Wastes time; you may enter the highest-concentration area |
| Re-enter before clearance | Gas may still be present |
| Assume the smell has gone = safe | Gas may have dispersed from one area but not another |
| Use an open flame to check for leaks | This is how explosions happen |
| Leave the door open and stay inside | Inadequate — you must leave |
Return to the building only after:
If a gas appliance caused the leak, it must be repaired or replaced by a certified gas engineer before it is used again.
LPG behaves differently from natural gas in a leak scenario:
| Situation | Action |
|---|---|
| Smell gas indoors | No switches; open windows; evacuate; call emergency number |
| Gas alarm sounds | Treat as real; follow evacuation procedure |
| Meter accessible en route | Turn stopcock 90° off, then leave |
| Outside the building | Call gas emergency number; do not re-enter |
| Leaking LPG cylinder | Turn cylinder valve off if possible; keep outside; call emergency services |
| After professional clearance | Return only when explicitly told safe |
| Annual maintenance | Have all gas appliances certified annually |
This guide provides general safety information about gas leak response. Always follow instructions from local emergency services and qualified gas engineers. Gas safety regulations and emergency contact numbers vary by country and region — know your local numbers before an emergency occurs.
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