What Does a Gas Safety Check Involve

A gas safety check is a formal inspection of all gas appliances, pipework, flues, and ventilation systems in a property. It is carried out by a Gas Safe registered engineer to confirm that everything is operating safely and in line with UK gas safety regulations. These checks are essential for landlords, recommended for homeowners, and vital in any property where gas is used for heating, hot water, or cooking.

The goal of a gas safety check is not to service or repair appliances, but to ensure that they are installed correctly, functioning properly, and not leaking gas or producing dangerous emissions such as carbon monoxide. It is a preventive measure designed to catch issues before they become hazardous.

Appliance Inspection and Function Testing

During a gas safety check, the engineer will assess each gas appliance in the property, such as the boiler, hob, gas fire, or water heater. They will check that each appliance is burning gas safely and efficiently, using the correct gas-to-air ratio, and that the flame pattern is steady and clean. A poor flame colour or inconsistent flame can indicate a fault or incomplete combustion, which may lead to carbon monoxide exposure.

The engineer will also test the appliance’s safety devices — such as flame supervision devices, pressure release valves, or cut-off switches — to ensure they operate correctly under fault conditions. The focus is on identifying anything that could present a safety risk, such as leaks, carbon monoxide release, or poor ventilation.

Gas Pipework and Tightness Testing

Another key part of a gas safety check is testing the pipework that delivers gas to your appliances. The engineer will conduct a tightness test to detect any gas leaks within the property’s system. This involves shutting off all appliances, pressurising the gas system slightly, and monitoring it to see if pressure drops — which would indicate a leak.

The engineer will also inspect the physical condition of the pipework, looking for signs of corrosion, damage, or poor installation. This ensures that the entire supply system is intact and able to deliver gas safely without the risk of escaping fuel or loss of pressure.

Flue and Ventilation Assessment

Every gas appliance that burns fuel needs to safely discharge the by-products of combustion. The engineer will inspect the flue or chimney connected to each appliance to make sure that it is properly installed, unblocked, and capable of expelling gases like carbon monoxide out of the building. Blocked or damaged flues can allow dangerous gases to enter the living space, which is why this step is critical.

They will also check the surrounding ventilation — such as air bricks or extractor fans — to confirm that there is enough airflow to support safe combustion. Appliances that burn fuel in a confined or poorly ventilated area pose a serious risk of carbon monoxide buildup, so ensuring proper air circulation is a key part of the inspection.

The Gas Safety Record

At the end of the check, the engineer will complete a Gas Safety Record (often called a CP12 in rental properties) which outlines the results of the inspection. It will detail each appliance checked, any faults found, whether the system passed the tightness test, and any recommendations or required repairs. For landlords, this record is a legal requirement and must be given to tenants within 28 days of the check, or before a new tenancy begins.

Homeowners are not legally required to have this document, but it is useful for record keeping and can be valuable when selling the property, applying for insurance, or tracking the performance of your gas appliances over time.

Who Needs a Gas Safety Check?

Gas safety checks are legally required for landlords in the UK under the Gas Safety (Installation and Use) Regulations 1998. Every rented property with a gas supply must undergo an annual gas safety inspection carried out by a Gas Safe registered engineer. This applies to private landlords, housing associations, local councils, and managing agents.

For homeowners, gas safety checks are not a legal obligation but are strongly recommended — especially if the boiler, fire, or gas hob is more than a few years old or if the property hasn’t been serviced recently. These checks are also a smart move before buying or selling a home, as they help identify hidden faults that could become expensive or dangerous later on.

How Long a Gas Safety Check Takes

The length of a gas safety check depends on the number of gas appliances in the property, their condition, and ease of access. In a typical home with a boiler and a hob, the check can take around 30 to 60 minutes. If additional appliances such as gas fires, water heaters, or cookers are present — or if issues are found that need further investigation — the visit may take longer.

It’s important that the engineer has clear access to each appliance, the gas meter, and any flues or vents. Obstructed areas can delay the inspection and may require a return visit if something cannot be checked properly on the day.

What Happens If Something Fails the Check

If an appliance or part of the gas installation is found to be unsafe during the check, the engineer is legally required to make it safe. This might mean disconnecting the appliance, issuing an “Immediately Dangerous” or “At Risk” warning, and advising on next steps. In most cases, you’ll be given a written report and a recommendation for repair or replacement.

Appliances classed as “Immediately Dangerous” must not be used until the fault is fixed. This includes issues like serious gas leaks, blocked flues, or appliances emitting carbon monoxide. Engineers will usually cap off the gas supply to that appliance on the spot to protect occupants.

Difference Between a Safety Check and a Service

A gas safety check is a visual and functional inspection to ensure appliances meet basic safety standards. It checks for leaks, correct installation, adequate ventilation, and safe combustion. It does not include internal cleaning or adjustments to improve performance.

A boiler service, by contrast, involves removing the boiler casing, cleaning internal parts, checking components like the burner and heat exchanger, and ensuring optimal performance. While both are important, they serve different purposes. Some engineers offer a combined visit that includes both, which can be cost-effective and convenient.

Keeping Records and Staying Compliant

After the gas safety check, the Gas Safety Record should be kept safely for at least two years. Landlords must provide a copy to existing tenants within 28 days and to new tenants before they move in. For short-term lets, this still applies — even if the tenancy is only for a few weeks.

Homeowners may not be legally required to hold a certificate, but it can be a valuable document if you’re ever asked to provide proof that the property is safe. This could be requested by a surveyor, insurance company, or future buyer.

Final Word

A gas safety check involves a full inspection of your gas appliances, pipework, flues, and ventilation to ensure everything is safe, compliant, and operating as it should. It helps prevent leaks, carbon monoxide exposure, and other risks associated with faulty gas systems. Whether you’re a landlord, homeowner, or just want peace of mind, having a Gas Safe registered engineer carry out regular checks is one of the most effective ways to protect your household and meet your legal responsibilities.