Many homeowners in Surrey and London believe that a carbon monoxide (CO) alarm will warn them about any gas-related danger — including a natural gas escape.
This is a common misunderstanding, and relying on the wrong detector can put your property and family at risk.

This guide from Certificates4UK Ltd explains the difference between CO alarms and gas leak detectors, what each device is designed to sense, and how to stay fully protected in your home.

No, a CO Alarm cannot detect a Gas Leak.

A carbon monoxide alarm is designed for one purpose: detecting carbon monoxide.
It cannot detect:

• Natural gas (methane)
• LPG (propane or butane)
• Gas escaping from boilers, cookers, or pipework
• Unburnt fuel of any kind

This means a CO alarm will not activate during a natural gas leak. If there is a gas escape in your home, your CO detector will remain silent.

What a CO Alarm Detect

Carbon monoxide is a colourless, odourless gas produced when fuel is burned incompletely. Common causes include:

• Blocked or damaged boiler flues
• A boiler burning with poor combustion
• Poor ventilation
• A sooted or cracked heat exchanger

CO exposure is dangerous because you cannot see, smell, or taste it — which is why a working CO alarm is essential in every UK home.

What Detects a Natural Gas Leak?

To detect a natural gas or LPG escape, you need a gas leak detector, not a CO alarm.

Gas Leak Detector Senses:

• Methane (UK mains gas)
• LPG (propane/butane)

CO Alarm Senses:

• Carbon monoxide only

These gases are chemically different, which is why they require completely separate detectors.

Why the Confusion Happens

Many people assume that a “gas alarm” refers to all gases. In reality:

• Natural gas does not contain carbon monoxide
• CO is created only when fuel burns incorrectly
• A gas leak is unburnt fuel, meaning no carbon monoxide is produced

This is why a CO alarm will not trigger during a gas escape.

Best Safety Setup for Homes in Surrey & London

To ensure full protection in your home, we recommend:

1. CO Alarm

Install near boilers, gas fires, and bedrooms—Detects carbon monoxide from faulty combustion.

2. Gas Leak Detector

Install in kitchens, boiler rooms, or utility areas to detect unburnt natural gas or LPG.

3. Annual Boiler Service

A yearly boiler service ensures correct combustion and checks for leaks.
Book your service:
https://www.certificates4uk.co.uk/boiler-service

4. Know the Gas Emergency Number

If you smell gas, turn off your supply at the meter and call the National Gas Emergency Service:

0800 111 999
Official government guidance:

https://www.nationalgas.com/safety-and-emergencies)

Need a Safety Inspection in Surrey or London?

Certificates4UK Ltd provides:

• Gas safety inspections (Gas Safe with CP12)
• Boiler servicing and emergency repairs
• Gas leak diagnostics
• Carbon monoxide testing
• EPC and EICR services for landlords and homeowners