How Gas Leak Detectors Work

Gas Detectors vs. Carbon Monoxide Detectors

This is the most common point of confusion: a carbon monoxide (CO) detector does not detect natural gas leaks. They measure different things entirely.

• Carbon monoxide detectors sense CO, an odorless byproduct of incomplete combustion. Required by law in most states.
• Combustible gas detectors sense methane (natural gas) and propane. Not typically required by code, but available for residential use.

If you're concerned about gas leaks specifically, you need a combustible gas detector — having a CO detector alone won't help.

Types of Combustible Gas Detectors

There are three main sensing technologies:

• Semiconductor sensors — the most common in consumer models. An element changes electrical resistance when exposed to gas. Affordable but can trigger false alarms from cooking fumes or aerosol sprays.
• Catalytic bead sensors — used in professional-grade detectors. Gas combusts on a heated bead, changing its resistance. More accurate but more expensive and the sensor wears out over time.
• Infrared sensors — measure how gas absorbs infrared light. Most accurate and longest-lasting, but typically found in industrial equipment rather than consumer models.

For home use, semiconductor models are the practical choice. They're widely available, affordable, and reliable enough for residential detection.

Where to Place Them

Placement matters because gas behavior depends on the type:

• Natural gas (methane) is lighter than air and rises. Place detectors high on the wall or ceiling, near gas appliances — kitchen stove, furnace, water heater, gas dryer.
• Propane is heavier than air and sinks. Place detectors low, near the floor if you use propane.
• Don't place detectors directly next to cooking surfaces (too many false alarms), in bathrooms (humidity interference), or in garages (exhaust fumes).

A good starting point: one detector near your furnace/water heater and one in the kitchen, both positioned according to the gas type you use.

Battery vs. Plug-In vs. Smart Detectors

• Battery-powered — easy to place anywhere, but you need to remember to replace batteries (usually annually).
• Plug-in with battery backup — always-on power with backup if the outlet fails. Most reliable for a "set and forget" approach.
• Smart detectors — connect to Wi-Fi, send phone alerts, and can integrate with smart home systems. Useful if you travel or want remote monitoring. More expensive.

All three types are effective at detection. The best detector is the one you'll actually install and maintain.

What the Alarm Means

When a combustible gas detector alarms:

• Treat it as real until proven otherwise — false alarms happen but the stakes are too high to assume.
• Follow the same steps as smelling gas — leave the building, don't create sparks, call 911 from outside.
• Check the detector after the all-clear — if it alarms repeatedly with no confirmed leak, it may need replacement or repositioning away from cooking areas.

See our guide on what to do if you smell gas for the complete emergency procedure.