What Appliances Get Checked During a Gas Safety Inspection?

A gas safety inspection is a formal assessment of all gas appliances, pipework, flues, and ventilation systems within a property, carried out by a Gas Safe registered engineer. Gas Safe is the official gas registration body in the UK, replacing CORGI in 2009. Only engineers on the Gas Safe Register are legally permitted to work on gas appliances in the UK.

For landlords, the inspection results in a Gas Safety Record, commonly known as a CP12 certificate, which documents the findings of the inspection and confirms whether each appliance and component meets current safety standards. The Gas Safety (Installation and Use) Regulations 1998 require landlords to have this inspection carried out every 12 months for all rental properties that contain gas appliances. The certificate must be provided to existing tenants within 28 days of the inspection and to new tenants before they move in.

A gas safety inspection is not the same as a boiler service. A service involves cleaning, calibrating, and maintaining the appliance to keep it running efficiently. An inspection assesses whether it is safe. Both are important, and both should be carried out annually, but they serve different purposes, and one does not replace the other.

Only a Gas Safe registered engineer is legally permitted to carry out a gas safety inspection and issue a Gas Safety Record. Every Gas Safe engineer carries a card showing their registration number and the specific appliance types they are qualified to work on.

Before allowing an engineer into your property, you or your tenant has the right to check their Gas Safe card. This isn't a formality. Working on gas appliances without Gas Safe registration is a criminal offence, and any certificate issued by an unregistered engineer has no legal validity.

The Gas Safe Register card also shows which appliance categories the engineer is qualified to work on. An engineer qualified for domestic boilers is not automatically qualified for commercial catering equipment or LPG appliances, the card specifies what they can legally work on.

1. Gas Boiler (Central Heating Boiler)

The boiler is the most significant gas appliance in the majority of rental properties and receives the most detailed assessment during the inspection.

What the engineer checks:

Burner operation and combustion: The engineer checks that the burner ignites correctly, operates steadily, and shuts down cleanly. They assess the quality of the flame — a healthy gas flame burns blue and steady. A yellow, orange, or irregular flame indicates incomplete combustion and is a safety concern that requires investigation.

Flue integrity and operation: The flue carries combustion gases, including carbon monoxide, away from the appliance and out of the building. The engineer checks that the flue is correctly connected, undamaged, adequately supported, and terminated in an appropriate location outside the building. Any signs of flue gas spillage inside the habitable space are treated as an immediate safety concern.

Combustion analysis (flue gas test): Using a calibrated flue gas analyser, the engineer measures the concentration of gases in the flue, including carbon dioxide, carbon monoxide, and excess oxygen. The readings are compared against acceptable limits for the appliance type. Abnormal combustion readings indicate a problem with the heat exchanger, burner, or air supply that could produce dangerous levels of carbon monoxide.

Gas pressure and gas rate: The engineer measures the gas pressure at the appliance and checks that the gas rate, the volume of gas consumed during operation, matches the manufacturer's specification. An incorrect gas rate can indicate a fault with the gas valve, injectors, or heat exchanger.

Ventilation: Boilers require an adequate supply of fresh air for safe combustion. The engineer checks that any required ventilation openings are present, unobstructed, and of the correct size for the appliance. Room-sealed (balanced flue) boilers draw combustion air from outside, so this check applies primarily to open-flued appliances.

Safety devices: The engineer tests the operation of the boiler's built-in safety devices, including the overheat thermostat, pressure relief valve, and any frost protection features. These must operate correctly to prevent unsafe conditions from developing.

Visual condition: The overall condition of the boiler is assessed visually, including the casing, controls, pipework connections, and any signs of corrosion, water leaks, or heat damage. While a visual check is not a substitute for a full service, obvious deterioration that creates a safety risk is flagged.

2. Gas Cooker or Gas Hob

If the property includes a gas cooker, range cooker, or gas hob, whether freestanding or built-in, it is inspected as part of the gas safety check.

What the engineer checks:

Stability and installation: Freestanding cookers must be correctly installed with an adequate flexible connection (bayonet fitting or approved flexible hose) and must be stable. A cooker that can be pulled forward and disconnected by a tenant cooking is a known cause of gas incidents.

Burner operation: Each burner is operated to confirm it ignites cleanly and burns with a correct, steady flame. Burners that do not ignite, produce irregular flames, or fail to shut off cleanly when turned to the off position are a safety concern.

Ignition system: The automatic ignition system, spark or glow ignition, is tested on each burner. A burner that requires repeated attempts to ignite or that fails to ignite at all may indicate a blocked injector or ignition electrode fault.

Flame supervision devices (FSDs): Modern gas cooker burners are fitted with flame supervision devices, thermocouples, or flame rectification sensors that shut off the gas supply if the flame goes out. The engineer checks that FSDs are present and operating correctly on all applicable burners. Missing or faulty FSDs are a safety concern because an extinguished burner without an FSD will continue releasing unburned gas.

Flexible hose condition: The flexible connection between the cooker and the fixed gas pipework is inspected for signs of damage, deterioration, kinking, or age. Flexible connections have a maximum recommended service life and must be replaced when they show signs of wear or reach their expiry date (typically printed on the hose itself).

Ventilation: The kitchen must have adequate ventilation for safe gas appliance operation. The engineer checks that windows, air bricks, or mechanical extraction are present and adequate.

3. Gas Fire or Gas Room Heater

Gas fires — both decorative and functional — and gas room heaters represent one of the highest-risk categories of domestic gas appliance. A disproportionate number of fatal gas incidents involve open-flued gas fires in older properties.

What the engineer checks:

Flue pull test Open-flued gas fires draw combustion air from the room and expel combustion gases up through a chimney or flue. The engineer carries out a spillage test — also called a flue pull test — to confirm that combustion gases are being safely drawn up the flue rather than spilling into the room. This test is critical for identifying a blocked or inadequate flue that could allow carbon monoxide to accumulate in the living space.

Flame picture and combustion The fire is operated at full output and the flame picture is assessed. A yellow, lazy, or irregular flame in a gas fire is a significant safety indicator and warrants further investigation.

Ventilation Open-flued gas fires require specific minimum ventilation openings in the room in which they are installed. The engineer checks that these openings are present, unobstructed, and of the correct size. Blocking a ventilation air brick — a common occurrence when tenants try to reduce draughts — can create dangerous carbon monoxide conditions with an open-flued appliance.

Fireguard and clearances The physical clearances around the fire — to walls, flooring, and combustible materials — are checked against the appliance installation requirements.

Condition and safety devices The overall condition of the fire is assessed, including the condition of the burner, the control valve, and any safety cut-off devices. Older gas fires that lack modern safety features may be classified as unsafe for continued use.

4. Gas Central Heating System (Pipework, Radiators, and Controls)

Beyond the boiler itself, the central heating system's pipework, radiators, and controls form part of the gas safety inspection.

What the engineer checks:

Visible pipework: All accessible gas pipework within the property is visually inspected for signs of corrosion, mechanical damage, inadequate support, or inappropriate materials. Flexible corrugated stainless steel tubing (CSST) and copper pipework are both acceptable, but older lead pipework or non-approved materials are a concern.

Gas tightness test: The engineer carries out a gas tightness test on the entire gas installation, not just the appliances. This involves pressurising the gas pipework and monitoring whether the pressure holds over a set period. A pressure drop indicates a gas leak somewhere in the system, which must be traced and repaired before the installation can be certified as safe. This is one of the most critical tests carried out during the inspection; a gas leak that goes undetected is a fire and explosion risk as well as a potential source of carbon monoxide.

Meter and emergency control valve: The gas meter installation and the emergency control valve (ECV), the isolation valve typically located at or near the meter, are checked to confirm they are accessible, clearly labelled, and operating correctly. Tenants must be able to locate and operate the ECV in an emergency.

5. Gas Water Heater or Instantaneous Hot Water Heater

Properties that use a standalone gas water heater, rather than a combination boiler, have the water heater inspected separately.

What the engineer checks:

Flue and combustion: As with a boiler, the flue condition, connection, and termination are checked, and a combustion analysis is carried out where accessible.

Operation and controls: The water heater is operated, and its control sequence, ignition, temperature regulation, and shut-down are assessed for correct function.

Water flow and temperature: The water outlet temperature is checked to confirm it is within safe limits. Instantaneous water heaters set too high present a scalding risk.

6. Gas Tumble Dryer (Where Present)

Mains gas tumble dryers are less common in residential properties, but are inspected where present.

What the engineer checks:

Flue and exhaust: The exhaust duct is checked for correct installation, condition, and termination. A blocked or incorrectly terminated duct can cause combustion gases to spill into the property.

Burner operation: The burner is operated, and the flame quality is assessed as with other gas appliances.

When a gas appliance is inspected, the engineer classifies its safety status using one of three Immediately Dangerous (ID), At Risk (AR), or Not to Current Standards (NCS) classifications — or confirms it as Safe to Use.

Immediately Dangerous (ID):

An appliance or installation component classified as Immediately Dangerous poses an immediate risk of injury to any person. The engineer is required to take action to prevent use — typically by disconnecting or isolating the appliance and must advise the landlord or occupant in writing that the appliance must not be used until it has been repaired or replaced.

Examples of Immediately Dangerous findings include a confirmed gas leak, a blocked or disconnected flue, a severely cracked heat exchanger, or a faulty gas valve that cannot be shut off.

At Risk (AR):

An appliance classified as At Risk is not immediately dangerous but has a fault or defect that, if left unaddressed, could become dangerous. The engineer strongly recommends that the appliance be taken out of use until it is repaired.

Examples include a deteriorating flexible hose, a faulty flame supervision device, or ventilation that is marginally below the required minimum.

Not to Current Standards (NCS):

An NCS classification means the appliance or installation does not meet current technical standards but does not present an immediate or near-term danger. This is typically applied to older appliances that were installed to standards that have since been updated.

NCS appliances are not required to be immediately taken out of service, but should be upgraded when practicable.

Safe to Use:

The appliance meets current safety requirements and is fit for continued use. This is the outcome required for all items on a property before a Gas Safety Record (CP12) can be issued as satisfactory.

If any appliance is classified as Immediately Dangerous, the engineer will disconnect it before leaving the property. The Gas Safety Record will record the finding, and the appliance must be repaired or replaced, and re-inspected, before it can be returned to use.

As a landlord, you have several obligations following a failed inspection:

1. Arrange repairs promptly — particularly for any ID classification, where the appliance must not be used until it is made safe
2. Inform your tenant of the situation in writing, including which appliances are not to be used
3. Arrange a follow-up inspection once repairs are complete to confirm the appliance is now safe
4. Update the Gas Safety Record to reflect the repaired status

For appliances classified At Risk, the same urgency applies even though the engineer may not have been required to disconnect the appliance. Acting quickly protects your tenants and protects you legally.

Understanding the limits of the gas safety inspection is as important as understanding what it covers.

The inspection does not cover:

• Servicing or maintenance of any appliance — cleaning, calibrating, or replacing worn components is a service task, not an inspection task. A boiler that passes its safety inspection may still be running inefficiently due to scale build-up or worn components — only a service will address this.
• Oil or LPG appliances — a standard gas safety inspection covers mains natural gas installations only. Oil boilers, LPG appliances, and solid fuel heating systems are subject to separate inspection and certification requirements.
• Electrical components of gas appliances — the electrical supply to a boiler or gas fire is not assessed during a gas safety inspection. Electrical safety is covered under a separate EICR.
• Tenant-owned appliances — unless specifically agreed with the landlord, tenant-owned gas appliances are the tenant's responsibility.

Do I need a gas safety inspection if my property only has a gas hob and no boiler? Yes. Any property with gas appliances, regardless of type, requires an annual gas safety inspection. A property with a gas hob and an electric heating system still requires a Gas Safety Record covering the hob, the gas pipework, and the meter.

What if my tenant refuses to allow access for the inspection? You must give at least 24 hours' written notice before the visit. If a tenant repeatedly refuses access, document all attempts in writing and seek legal advice. You cannot force entry, but you must demonstrate that you have made every reasonable effort to carry out the inspection. Failure to have a valid Gas Safety Record is your legal liability regardless of a tenant's refusal.

Can I use any Gas Safe registered engineer? Yes, provided their Gas Safe registration covers the specific appliance types in your property. Always verify the engineer's card or check their registration online before they begin work.

Does a new build property need a gas safety inspection? A new build comes with commissioning certificates for its gas appliances. However, once the property is let, the annual gas safety inspection obligation begins from the date of the first tenancy. Many landlords arrange the first inspection to coincide with or just before the first tenancy begins.

Is a gas safety record the same as a boiler warranty inspection? No. Some boiler manufacturers require annual servicing to maintain a warranty, but this is a separate commercial obligation between the landlord and the manufacturer. The Gas Safety Record is a statutory legal requirement regardless of whether any warranty is in place.

What happens if my tenant smells gas? Your tenant should call the National Gas Emergency Service on 0800 111 999 immediately, leave the property, and not operate any electrical switches. Do not re-enter the property until it has been declared safe. As a landlord, you should arrange an emergency inspection and any necessary repairs before the property is reoccupied.