What Does a Gas Safety Check Include? And How It Differs From a Boiler Service
What the Engineer Actually Tests
A Regulation 36 gas safety check covers every landlord-provided gas appliance and flue in the property. The engineer works through a set of standard tests on each item:
- Gas tightness: testing the installation pipework for leaks using a manometer
- Burner pressure and gas rate: checking the appliance is operating at the correct input
- Flue flow: confirming exhaust gases are drawing correctly through the flue
- Spillage test: detecting whether combustion products are escaping into the room
- Combustion gas analysis: measuring CO and CO2 levels in the flue gases
- Safety device operation: testing thermocouples, flame supervision devices, and overheat protection
For a single-boiler property, the check typically takes 20 to 40 minutes. Add a gas hob and a gas fire and you're looking at 40 to 60 minutes. The engineer then completes a Landlord Gas Safety Record (CP12) documenting every appliance, the test results, any defects found, and remedial action taken.
The Three Defect Classifications
When an engineer finds a problem, they classify it under the Gas Industry Unsafe Situations Procedure (IGEM/G/11):
Immediately Dangerous (ID): The appliance poses a direct danger to life or property. The engineer must disconnect the gas supply with the occupant's consent and attach a Danger Label. If consent is refused, the engineer notifies the gas supplier, who can turn off the external supply.
At Risk (AR): The appliance has a defect that could become dangerous. The engineer turns it off with consent and attaches a Warning Label. Repairs are needed before the appliance can be used again.
Not to Current Standards (NCS): The appliance doesn't meet today's installation standards but isn't an immediate or potential hazard. It's noted on the record with a recommendation for future upgrade.
As a landlord, ID and AR findings require action before the tenant can use the appliance again. You'll need a Gas Safe engineer to carry out repairs, re-test, and issue a new passing record.
How a Gas Safety Check Differs From a Boiler Service
This is the most common point of confusion. They are two different things with two different legal purposes:
| Gas safety check | Boiler service | |
|---|---|---|
| Legal basis | GSIUR 1998 Regulation 36 | Manufacturer recommendation |
| Purpose | Confirm the appliance is safe to use | Maintain efficiency and longevity |
| Frequency | Annual (statutory requirement) | Annual (recommended, not statutory) |
| Output | Landlord Gas Safety Record (CP12) | Service report or logbook entry |
| Covers | All gas appliances and flues | Typically one boiler |
An engineer can do both in a single visit — and many offer combined packages. But the service invoice does not replace the CP12 unless it contains all nine statutory fields required by Regulation 36(3)(c). A boiler service logbook entry alone doesn't satisfy your annual check obligation.
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Why the Distinction Matters Financially
A standalone gas safety check for a single appliance costs between £45 and £90 across most of England. A combined boiler service and safety check typically runs £90 to £230, depending on region. London and the South East sit at the top of that range.
If you're paying for a combined visit, make sure you receive two distinct outputs: a signed service report (for your maintenance records) and a completed Landlord Gas Safety Record (for your compliance file). Both serve you, but only one is the legally prescribed document.
Our Gas Safety Compliance Guide walks through the full inspection process, including how to read your CP12 results and what to do when a defect classification lands.
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