Landlord Gas Safety Checks: CP12, Legal Requirements, and What Gas Safe Engineers Must Inspect

Landlord gas safety checks are one of the most frequently performed jobs in the UK gas industry — hundreds of thousands of properties require an annual check under the Gas Safety (Installation and Use) Regulations 1998. Every Gas Safe registered engineer needs to know exactly what the check covers, what records must be kept, what constitutes a dangerous appliance, and how to handle the paperwork correctly. This guide covers the legal obligations for landlords, the inspection procedure, safe/at-risk/immediately dangerous classifications, the Gas Safety Record (GSR, commonly called CP12), and what happens when a dangerous appliance is found.

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The Legal Basis: Gas Safety (Installation and Use) Regulations 1998

Regulation 36 of the Gas Safety (Installation and Use) Regulations 1998 imposes a duty on landlords to:

• Arrange an annual gas safety check of every gas appliance and flue in their residential properties
• Ensure the check is carried out by a Gas Safe registered engineer
• Keep a record (the Gas Safety Record) for at least two years
• Provide a copy to each existing tenant within 28 days of the check being completed
• Provide a copy to new tenants before they occupy the property

The regulations apply to private landlords, housing associations, and other providers of rented residential accommodation. They do not apply to owner-occupiers, commercial premises (which are subject to different regulations), or communal areas in blocks of flats (where the building owner/managing agent has separate duties).

Failure to comply with Regulation 36 is a criminal offence. Landlords can face unlimited fines or imprisonment. HSE actively prosecutes non-compliant landlords, particularly following gas-related incidents. Engineers who carry out checks that do not meet the required standard may face removal from the Gas Safe Register.

Who Can Carry Out a Landlord Gas Safety Check?

The check must be carried out by an engineer registered with Gas Safe Register for the relevant appliance type. Gas Safe registration is appliance-specific — an engineer may be registered for domestic natural gas boilers but not for LPG appliances, or for commercial catering equipment but not domestic installations. Engineers must verify their registration covers the appliances present in the property before carrying out the check.

Gas Safe registration can be verified via the Gas Safe Register website using the engineer's ID card number — landlords and tenants are entitled to check this before allowing access.

What the Check Must Cover

The landlord gas safety check must inspect every gas appliance and flue in the property. For a typical residential property, this includes:

Gas Boiler / Central Heating System

• Boiler operation — fire up, check burner operation, check lockout/error codes
• Gas pressure at the appliance — test point reading (inlet and burner pressure where applicable)
• Gas rate — check against the appliance data plate using a meter test
• Flue integrity — visual inspection; spillage test using a smoke match or smoke pellet for open-flued appliances; combustion analysis for room-sealed appliances where access is provided
• Ventilation — verify permanent ventilation provisions are present and unobstructed (for open-flued appliances)
• Safety devices — check overheat thermostat, pressure relief valve, and thermostatic controls are functional
• Visible pipework and connections — check for corrosion, damage, or inadequate support

Gas Fires and Wall Heaters

• Operation check — ignition, burner pattern, heat output
• Flue and spillage test — critical for older open-flued fires where flue blockage is common
• Ventilation provision — open-flued fires in particular require adequate permanent ventilation
• Flame failure device check — the ODS (oxygen depletion sensor) on flueless fires must function correctly
• Condition of the fire and firebox — damaged or corroded components may affect safety

Gas Cookers and Hobs

• Operation of all burners
• Ignition system
• Flexible hose condition (if used) — a corrugated stainless steel connector or approved flexible hose must be used; PVC-covered hoses are not acceptable for gas
• Stability (cookers must be secured or have an anti-tilt device if on a pedestal base)

Pipework

• Visual inspection of all visible gas pipework — for corrosion, physical damage, adequate support, painting over fittings
• Tightness test — a let-by test and pressure tightness test on the installation using a manometer or electronic gas analyser

The Tightness Test

Every gas safety check must include a tightness test of the gas installation. The procedure:

1. Turn off all gas appliances (all burners/pilots off)
2. Connect a manometer to the test point on the meter outlet (or use a pressure gauge at an appropriate test point)
3. Note the working pressure and allow 2 minutes for temperature equilibration
4. Shut the emergency control valve (ECV)
5. Record the initial pressure — let-by test: if pressure falls within 1 minute with ECV closed, the ECV itself may be passing (let-by). If pressure is stable, proceed.
6. Open the ECV; re-pressurise the system to working pressure; close the ECV
7. Allow 2 minutes, then monitor for a further 2 minutes. Any pressure drop indicates a leak in the installation pipework
8. If no pressure drop: tightness test passed
9. If pressure drops: locate and repair the leak before proceeding

A tightness test that reveals a leak must be investigated and the leak repaired before the Gas Safety Record can be issued. An engineer who issues a record on a leaking installation is in breach of Gas Safe Register standards.

Appliance Classification: Safe / AR / ID

Every appliance inspected is classified as one of three categories:

Safe (S)

The appliance is operating safely and in accordance with the relevant standard. No action required.

At Risk (AR)

The appliance has a fault or defect that makes it potentially unsafe but is not immediately dangerous. The appliance may be left in service, but the landlord must be informed and the defect must be remedied within an agreed timeframe. Examples: a cracked firebox that does not affect current operation but will deteriorate; a minor flue spillage under certain conditions; inadequate ventilation that causes marginal conditions.

Immediately Dangerous (ID)

The appliance presents an immediate risk to life if left in service. The engineer must:

1. Advise the landlord or tenant of the danger
2. Disconnect the appliance from the gas supply (or request the landlord arranges disconnection immediately)
3. Label the appliance with a "Do Not Use" warning label
4. Record the ID classification on the Gas Safety Record
5. Obtain the landlord's or tenant's signature acknowledging the danger and the disconnection

Engineers must not reconnect an ID-classified appliance themselves — they must advise that a competent person repairs or replaces the appliance and then reinspects it before return to service. Examples of ID appliances: boiler flue discharging combustion products into the property; gas fire with a blocked flue creating carbon monoxide risk; severe gas leak from an appliance.

Carbon Monoxide

Carbon monoxide (CO) from incomplete combustion is the gas industry's most lethal hazard. CO is colourless and odourless — it kills without warning. Engineers should carry a personal CO monitor whenever working in properties with gas appliances.

During a landlord gas safety check:

• Where combustion analysis equipment is available, check CO in the flue products for boilers and fires (CO should not normally exceed 0.04% — 400 ppm — in the flue; check against manufacturer's specification)
• If the CO monitor alarms during the inspection, treat this as a serious incident — ventilate the property, advise occupants to leave, identify the source
• A CO alarm must be present in any room with a solid fuel burning appliance in rented properties (Smoke and Carbon Monoxide Alarm (England) Regulations 2022) — though the regulations do not currently mandate CO alarms for gas appliances, Gas Safe Register guidance recommends advising landlords to fit them

The Gas Safety Record (CP12)

Following the check, the engineer issues a Gas Safety Record (GSR). Despite the common use of the term "CP12" — derived from a historical CORGI document — the official title is Gas Safety Record. It must contain:

• Address of the property
• Name and address of the landlord
• Date of inspection
• Description of each appliance and flue inspected
• Any defect identified and action taken or to be taken
• Confirmation of whether each appliance is safe/at risk/immediately dangerous
• Name, registration number, and signature of the Gas Safe registered engineer

The record must be issued as:

• Original to the landlord (retained for minimum 2 years)
• Copy to the tenant within 28 days (or on occupation for new tenants)
• Copy retained by the engineer's business records

Common Failures in Landlord Gas Safety Checks

HSE and Gas Safe Register audits identify recurring issues:

• Failure to conduct a tightness test — this is mandatory for every check
• Failure to check all gas appliances in the property — it is not acceptable to "skip" a kitchen hob because the tenant says it's not used
• Incomplete Gas Safety Record — missing appliance descriptions, engineer's registration number, or defect classification
• Failure to advise on CO risks or ID appliances
• Using CP12 forms that omit required fields — use only current Gas Safe-compliant templates
• Conducting checks outside the area of the engineer's Gas Safe registration (e.g., an engineer registered for natural gas only checking an LPG appliance)

Annual Check Timing

The check must be carried out within 12 months of the previous check. To avoid expiry gaps, Gas Safe Register allows the next annual check to be carried out up to 2 months before the anniversary — the new record is then dated the anniversary date (not the actual date of inspection if earlier) so the 12-month cycle is maintained. This "two-month window" lets engineers service and check at the same visit without creating a gap in the landlord's compliance record.

Products from APM

APM Electrics Plumbing stocks gas safety equipment including CO analysers, manometers, tightness test equipment, gas pressure gauges, and "Do Not Use" warning labels for ID appliances. Browse our gas collection for gas safety testing equipment and gas appliance components.

Visit us at APM Electricals, 24 Western Avenue, Acton, London, W3 7TZ or call 020 8896 0800 for trade and retail electrical and plumbing supplies.