Gas Safety Check: What Happens Step by Step in a London Property
If you are booking a gas safety check for the first time, or you are a London landlord arranging your first CP12 inspection, understanding exactly what the engineer does during the visit helps you prepare the property and ensures the inspection goes smoothly. This guide walks through every step.
What Is a Gas Safety Check and Who Carries It Out
A gas safety check, formally known as a Gas Safety Inspection and resulting in the issue of a Gas Safety Record (colloquially called a CP12), must be carried out by a Gas Safe registered engineer. Gas Safe is the UK statutory body that maintains the register of engineers qualified to work on gas appliances. Homeowners and landlords can verify any engineer they book by checking the Gas Safe Register website using the engineer name or registration number, or by asking the engineer to show their Gas Safe ID card on arrival. The card shows the engineer name, registration number, and the specific appliance types and work categories they are qualified to carry out.
For London landlords, a gas safety check is a legal requirement under the Gas Safety (Installation and Use) Regulations 1998 and must be renewed annually for every tenanted property. For homeowners, a gas safety check is not a legal requirement but is strongly recommended when purchasing a property or when the appliances have not been checked for several years. Mortgage lenders and solicitors involved in a property sale or remortgage in London sometimes request a current gas safety certificate as a condition of the transaction.
Step-by-Step: What the Engineer Does During a London Gas Safety Check
On arrival, the engineer will confirm the appliances to be checked. In a standard London property, this typically includes the boiler, any gas hob or gas cooker, and any gas fire. Each appliance must be checked individually, and the fee quoted should cover all appliances at the property. The engineer begins with the boiler, checking the gas supply pressure and flow rate at the appliance, confirming that the inlet pressure is within the specification for the appliance model. The flue or flue system is inspected to confirm it is intact, unobstructed, and correctly routed to terminate at an appropriate external position.
Each appliance is operated to confirm it lights correctly and that the burner flame is stable and of the correct colour (predominantly blue with small yellow tips on a correctly adjusted burner). A flue gas analysis is carried out using calibrated equipment to measure the carbon dioxide and carbon monoxide content of the flue gases, confirming that combustion is complete and that the appliance is not producing dangerous levels of carbon monoxide. Safety devices including the flame failure device, which shuts off the gas supply if the burner fails to light or the flame is extinguished, are tested to confirm they operate correctly.
For a gas hob or cooker, the engineer checks that each burner ignites and holds a stable flame, that the gas supply isolation valve operates, and that there are no signs of damage, corrosion, or gas leakage at the connection. For a gas fire, the flue or balanced flue arrangement is inspected, the fire is operated, and the spillage test is carried out to confirm that combustion gases are venting to the outside rather than spilling into the room.
What Happens After the Gas Safety Check in London
At the completion of the inspection, the engineer will discuss the findings with the householder or landlord. If all appliances and flue arrangements are satisfactory, a Gas Safety Record is issued with a result of Satisfactory. If any issues are found, the engineer will classify them and discuss the remedial action required. Issues classified as Immediately Dangerous are resolved by the engineer either carrying out a repair on the spot or, if that is not possible at the same visit, by disconnecting the appliance and capping the gas supply to it. Prestige Engineers carry out gas safety inspections across London and issue all records digitally, providing a copy to the London landlord and, where required, to the tenant at the completion of the visit.