Gas Safety Certificate and Inspection

Gas installations carry a real risk of fire, explosion and carbon monoxide poisoning, so most countries set rules for regular checks. The details differ from country to country. In some places landlords must arrange a check every year, while owner-occupiers are advised rather than required to do so. Other countries set fixed intervals of a few years for all homes. Your last inspection report usually states when the next check is due. If you are unsure, ask a registered gas engineer or your local building authority.

Apart from the regular intervals, an inspection is also needed in these situations:

• After a new boiler, cooker, hob or water heater is installed
• After gas pipework is altered, extended or moved, for example during a kitchen refit
• When a new build or renovation is completed, or the use of a room changes
• When you sell or let a property and the new owner or tenant wants proof that the installation is safe
• After a fault, a gas leak or any work on the pipework

When you finish a building project, check with your local building authority in good time which gas documents it will want to see. Do not assume it will ask for nothing. In a block of flats, the building management or owners' association looks after the shared pipework. The appliances and pipework inside your flat are your responsibility.

In a flat or a family house, the visit usually takes somewhere between half an hour and an hour. More appliances or longer pipe runs mean it takes longer. The engineer normally works through these steps:

1. Inspect the pipework from the main gas valve to each appliance. The engineer looks at fixings, corrosion and damage, and checks that pipes are not buried in walls where they should not be.
2. Check the appliance valves and the main isolation valve. They must be easy to reach, labelled and able to close fully.
3. Test joints, unions and flexible hoses for leaks with a gas detector or leak detection spray.
4. Check each appliance: the connection, the safety devices, how the flame burns and how flue gases are carried away.
5. Assess room ventilation and the air supply for combustion, especially for boilers and water heaters that take their air from the room.
6. Record the results and any defects in the report and explain them to you.

For a new installation or after major changes to the pipework, the engineer also carries out a pressure test, often called a tightness test. The pipework is pressurised and the engineer watches whether the pressure drops over the required time.

Checking a flat with a single hob is a very different job from inspecting a house with a boiler, a water heater and pipework running over several floors. The main factors that affect the effort, and therefore the cost, are:

• The number of appliances and branches in the pipework
• The length of the pipework and how easy it is to reach, for example behind kitchen units or above suspended ceilings
• Whether a pressure test or further measurements are needed
• Missing drawings or older pipework that has been altered many times without records
• Whether it is a routine check or an urgent visit after a fault

The chimney or flue is usually inspected separately by a chimney sweep or flue specialist. Some engineers can coordinate both visits, or add an electrical check at the same time. This is handy when you are finishing a building project or preparing to sell.

Only a qualified gas engineer who is registered or licensed for gas work in your country may carry out the inspection. A report from someone without that registration carries no weight with the authorities or your insurer. Feel free to ask for the engineer's registration number before the work starts and check that it is valid. In many countries you can look it up on an official register.

The engineer sorts any defects by how serious they are. With a serious fault, such as a gas leak, a faulty flue or a valve that does not close, the appliance must not be used until the fault is fixed. The engineer will usually disconnect it or label it as unsafe. Minor defects, such as missing pipe labels or a valve that is hard to reach, do not stop you using the installation. They still need fixing by the date the engineer gives. Repairs to gas pipework and appliances must always be done by a registered gas engineer, never by a layperson.

In practice, people often keep using an old rubber hose on the cooker for many years, or build a kitchen unit right over the gas valve. Both are simple things, yet they are among the most common points raised during an inspection.

Do not work on the gas installation yourself. You can still make the engineer's visit go smoothly:

• Clear access to the boiler, cooker, water heater and main gas valve
• Move anything that covers pipework or valves
• Have previous inspection reports, service records and appliance manuals ready
• Note anything that has bothered you, such as a flame that goes out, odd noises or a smell

Between inspections, have your boiler serviced as the manufacturer recommends, usually once a year before the heating season. A service and an inspection are not the same: the service is maintenance of the boiler, the inspection judges the safety of the whole gas installation. Keep the boiler room dry and ventilated and never block air vents. A carbon monoxide alarm near gas appliances is a sensible extra safeguard. If you smell gas, close the main valve, do not switch lights or appliances on or off, open windows, leave the building and call the gas emergency line of your supplier or network operator, or the emergency number 112.

Read the report while the engineer is still there, so you can ask about anything unclear. Check that it contains:

• The engineer's name, registration number and signature
• The property address and a full list of the appliances checked, with type and gas type
• A description of the pipework and the result of the leak test or pressure test
• A list of defects sorted by seriousness, with a deadline for fixing each one
• A clear conclusion on whether the installation is safe to use
• The date of the inspection and the date of the next check
• Proof of payment, kept with the report, ideally also as a digital copy