What is checked in a gas safety check?
A gas safety check examines every gas appliance and flue the landlord is responsible for against the four matters regulation 26(9) names: the effectiveness of the flue, the supply of combustion air, the operating pressure or heat input (or combustion performance), and the appliance operating safely. Each result is recorded appliance by appliance.
Reviewed by Jordan Valentine-Dunn, Gas Safe registered engineer · Portsmouth Gas Heating · Last reviewed September 2026
Four things, by law, on every gas appliance and flue the landlord is responsible for: the flue, the air supply, the operating pressure or heat input, and the appliance working safely. That list is regulation 26(9) of the Gas Safety (Installation and Use) Regulations 1998, and regulation 36(9) makes it the floor for a landlord's annual check rather than the ceiling. Everything else on this page hangs off those four.
What does a gas safety check include?
The four examinations regulation 26(9) names, carried out on every gas appliance and flue provided for the tenant's use, plus whatever else the engineer judges necessary before calling an appliance safe to use. HSE's Approved Code of Practice and guidance L56 sets out the tests and examinations behind each one in its Appendix 3, and that is what the table below describes.
| The check | What the engineer does | A pass looks like | A fail looks like |
|---|---|---|---|
| 26(9)(a) The effectiveness of any flue | Examines the flue to confirm it is complete, continuous, undamaged and adequately supported along its whole length, joints included, and that the terminal is correctly sited. On an open flue, runs a flue flow test and then a spillage test with the appliance connected and burning. | The flue carries the products of combustion outside, and the spillage test stays clear with the room at its worst: external doors and windows shut, extract fans and any tumble drier running. | Smoke leaving a terminal that is not the right one, a down draught or no flow at all, spillage that does not clear, a damaged, sagging or badly jointed flue, or a concealed flue with no hatches to examine it through. |
| 26(9)(b) The supply of combustion air | Checks the room or space has a permanent supply of air sufficient for safe combustion, taking account of the room volume, the location, type and size of air vents and air bricks, draught proofing, replacement windows or any other later change, and whether a room-sealed appliance's air inlet is correctly sited and unobstructed. | Purpose-provided ventilation is present, the right size for the appliance, unobstructed, and not something a tenant can close. | A vent blocked, sealed, covered or built over by later work, a vent that can be shut or is gauzed, or an open-flued appliance in a room that never had the ventilation it needs. |
| 26(9)(c) The operating pressure or heat input, or both | Measures the working gas pressure at the appliance, or the heat input at the meter, against the figure in the manufacturer's installation instructions or on the appliance data badge. Both may be needed where a burner has been modified or replaced, such as after a conversion from LPG to natural gas. | The reading matches the manufacturer's figure for that model, within the tolerance the instructions allow. | A reading outside the manufacturer's figure, or an appliance that cannot be adjusted back to it. |
| 26(9)(ca) Combustion performance, where (c) is not reasonably practicable | Where there is no meter or meter display to measure the heat input directly and the operating pressure cannot be measured, takes a combustion reading with an analyser at the appliance's test point instead. | The readings and the CO/CO2 ratio sit inside the manufacturer's commissioning figures for that model. | Readings or a ratio outside the manufacturer's figures, which sends the engineer back to the appliance rather than on to the next one. |
| 26(9)(d) Its operation so as to ensure safe functioning | Runs the appliance and checks that its gas controls and safety devices work: flame supervision, spillage monitoring devices such as atmosphere sensing devices and thermal trip bars, fan proving, high limit thermostats. Also checks the flame picture, that case seals are sealing, that the appliance is stable and securely fitted, and that it is gas tight. | Every safety device does its job, the flame picture is right for that appliance type, the case seals are intact and the appliance is secure and sound. | A safety device that is inoperative, disabled, or fails to danger; a yellow or orange flame where a blue one belongs; soot, scorching or heat damage; a missing case seal or sample point cap. |
Regulation 26(9) is written as a duty on anyone who works on a gas appliance, which is why the same four checks follow a repair or a service as well as an annual check. Regulation 36(9) then says a landlord's safety check shall include, but shall not be limited to, those four matters. A competent engineer usually does more, and the flame picture, case seals and stability checks in the last row come from L56's guidance on what safe functioning means in practice rather than from the words of the regulation itself.
What is checked on each type of appliance?
The same four examinations, done differently, because a room-sealed boiler, an open-flued gas fire, a flueless cooker and an instantaneous water heater fail in different ways. The engineer also needs the manufacturer's instructions for the specific model, since those give the settings and tolerances everything is judged against.
| Appliance | What is done on it | What commonly fails it |
|---|---|---|
| Boiler (combi, system or regular) | Usually room-sealed, so the flue is examined along its length and at the terminal, with inspection hatches needed where it runs through a ceiling or a void. Operating pressure or heat input is measured against the data badge, or combustion performance taken where that is not practicable. Case seals, safety devices and fan proving are checked, and the appliance is checked for stability and gas tightness. | Readings outside the manufacturer's figures, a flue that is damaged, sagging, inadequately clipped or badly jointed, a missing case seal or air inlet sample point cap, or a concealed flue with no means of examining it. |
| Gas fire or gas space heater | Often open-flued, so it gets a flue flow test and then a spillage test with the fire burning, the doors and windows shut and any extract fan running. The chimney, catchment space and closure plate are checked for debris and effective sealing, the room's ventilation is assessed, and the controls, radiants and flame supervision device are checked. | Spillage that does not clear, debris in the catchment space, a chimney shared with another appliance that was not designed for it, a damper or restrictor plate left free to obstruct the flue, or ventilation that has been covered over. |
| Cooker or hob | Flueless, so the room and its ventilation are assessed against the manufacturer's instructions and the ventilation standard. Flame supervision on the hob burners, oven and grill is checked, every burner is lit to see the flame picture as industry best practice, and the appliance is checked for stability, clearances and gas tightness. A free-standing cooker on a flexible connection needs a stability device fixed to the fabric of the building, such as a bracket or a chain. | A missing stability bracket or chain, a flame supervision device that does not shut the gas off, a burner running yellow, or a cooker in a room used as a bathroom or shower room, which regulation 30(1) does not allow unless the appliance is room-sealed. |
| Instantaneous water heater | Flue and ventilation are checked as for any flued appliance, with flue flow and spillage tests where it is open-flued, and the operating pressure or heat input is measured. The engineer also checks the safety control that shuts the heater down before combustion products build up in the room, because since 31 October 1998 an instantaneous water heater may only be installed if it is room-sealed or has one. | Spillage, ventilation inadequate for the room volume, an older heater with no such safety control, or one fitted in a bathroom or shower room without being room-sealed. |
One rule catches landlords out more than the rest. Regulation 30 bars a gas fire, space heater or water heater of more than 14kW gross heat input from a room used as sleeping accommodation unless it is room-sealed, and one of 14kW or less unless it is room-sealed or has a safety control that shuts it down before products of combustion build up. Regulation 36(11) puts that duty on the landlord directly, so a study or dining room turned into a bedroom can create a defect without anyone touching the appliance.
What else does the engineer look at?
The pipework, the meter and the emergency control valve, and the alarms the property is required to have, none of which are gas appliances. Regulation 26(9) applies to work on appliances and does not reach meters or installation pipework, so what happens to them on the day is partly a matter of what you ask for.
- Installation pipework. HSE states plainly that installation pipework is not covered by the annual gas safety check, and recommends that when you request the check you ask your Gas Safe registered engineer to test the whole gas system for soundness, including the pipework, and to examine it visually as far as is reasonably practicable. Worth asking for, and worth having written on the record.
- The tightness test. The soundness test on the installation is that check, taken at the meter. It is not one of the four statutory matters, but an installation that fails a tightness test is an immediately dangerous situation under the industry procedure, so an engineer who finds one is not finishing the visit as planned.
- Ventilation. Covered by the 26(9)(b) check on each appliance, and also by anything that has changed the room since: draught proofing, replacement windows, a new floor, a conservatory that has enclosed a flue terminal, a fan added to a room containing an open-flued appliance.
- Carbon monoxide alarms. In England, since 1 October 2022, a landlord must have a carbon monoxide alarm in every room used as living accommodation that contains a fixed combustion appliance, gas cookers excluded, and must repair or replace an alarm a tenant reports as faulty. That duty sits in the smoke and carbon monoxide alarm regulations rather than the gas regulations, so it is separate from the check, and HSE's line on alarms is that they are a useful back-up precaution and not a substitute for proper installation and maintenance.
- The meter and the emergency control valve. The valve has to be appropriately sited with adequate access, as near as reasonably practicable to where the gas supply pipe enters the property, readily accessible to the people living there, and protected against being operated by anyone else. A landlord is expected to make sure every tenant, new ones included, knows where it is and what to do in a gas emergency.
What must the gas safety record contain?
Nine items, set out in regulation 36(3)(c) and repeated in HSE's guidance on gas safety records. A record missing any of them is not the record the law asks for, which is worth knowing before you file one away.
| What the record must show | What that means in practice |
|---|---|
| The date on which the appliance or flue was checked | The date the work was actually done, which starts the 28 day clock for giving the tenant a copy. |
| The address of the premises at which the appliance or flue is installed | The property, including the flat or unit where that matters. |
| The name and address of the landlord, or of their agent | Who the record belongs to and who is answerable for acting on it. |
| A description of, and the location of, each appliance or flue checked | Appliance by appliance, with make, model and where it sits, so it is clear what was looked at and what was not. |
| Any safety defect identified | Written down even where the engineer put it right the same day. |
| Any remedial action taken | What was done about the defect, or what still needs doing and by whom. |
| Confirmation that the check complies with regulation 36(9) | The statement that the check examined the regulation 26(9) matters in the first table on this page. |
| The name and signature of the individual carrying out the check | The engineer personally, not only the business name. |
| The registration number of that individual, or of their employer | The Gas Safe registration number, which you can check against the Register. |
HSE's guidance adds a point that matters whenever a defect turns up: a safety check record should not be issued until all the required tests and examinations have been completed on all the relevant appliances and flues. A record handed over with an appliance still untested is not finished, whatever the header says.
How long does a gas safety check take, and what does it cost?
Neither has a fixed answer, and no official body publishes one. Time is set by how many appliances and flues there are, because each is examined and recorded separately, and by what the property makes easy: a single room-sealed combi in a hallway cupboard is quick, while an open-flued gas fire needing a flue flow test and then a spillage test with the fans running is not. Price moves the same way. There is no statutory fee, most engineers quote a base price for the first appliance and add for each extra one, and region moves the number as much as anything else.
What happens if an appliance fails?
It is recorded as a defect against that appliance, and what follows depends on how the engineer classifies it under the Gas Industry Unsafe Situations Procedure, the industry guidance every Gas Safe registered engineer works to. There are two unsafe categories, not three.
| Outcome | What it means | What the engineer does | What has to happen next |
|---|---|---|---|
| Pass | The appliance was examined against the regulation 26(9) matters and is safe to use. | Records the result against that appliance and moves on to the next one. | Keep the record, give the tenant their copy, and book the next check within 12 months. |
| At Risk (AR) | One or more recognised faults are present which could constitute a danger to life or property without further faults developing. Inadequate ventilation is the standard example. | With the responsible person's permission, turns the appliance off and attaches a Danger Do Not Use label, then issues a warning notice. In a small number of situations turning it off would not reduce the risk, so the notice says who to contact instead. | The fault is repaired by a Gas Safe registered engineer before the appliance is used again. |
| Immediately Dangerous (ID) | If operated, or left connected to the gas supply, an immediate danger to life or property. Broadly: installations that fail a tightness test, appliances that fail a spillage test, and appliances with serious flueing, ventilation or combustion deficiencies. | With permission, disconnects and seals the gas supply to the appliance, fits a Danger Do Not Use label and issues a signed warning notice. If permission is refused on natural gas, contacts the Gas Emergency Contact Centre, which can attend and make the situation safe. | The appliance is not used until the defect has been repaired. Using an appliance you know to be unsafe, or allowing its use, is an offence, and it must not be reconnected first. |
| Not to current standards | Advice rather than a defect category. Standards and manufacturers' instructions change over time, so an installation put in correctly years ago may not match what would be installed today, which does not by itself make it unsafe. The current procedure classifies unsafe situations as At Risk or Immediately Dangerous only. | Explains what has changed and why, and records it as advice rather than as a defect. | Nothing is legally required. Gas Safe Register's advice is that bringing an installation up to current standards is worth doing where the cost is reasonable, or when other work is happening anyway. |
A defect on a record is not a disaster, and a landlord who acts on one quickly stands in a better place than a landlord who never had a defect found. Keep the record showing the defect together with the evidence of the repair. HSE recommends keeping copies of the work done to rectify defects found by a safety check, and the two documents together tell the whole story to anyone who asks later.
What must a landlord do with the record?
Give a copy to each existing tenant within 28 days of the date of the check, give any new tenant a copy before they occupy the property, and keep the record until two further checks have been carried out on that appliance or flue. Regulation 36 sets all three, and the retention rule can run longer than two years, because it counts checks rather than months.
- Existing tenants: a copy within 28 days of the date of the check. Where a tenant's right to occupy runs for 28 days or less, the record may be prominently displayed in the property instead.
- New tenants: a copy of the last record for each appliance and flue before they occupy the premises, not after. Before a new lease starts, the checks must have been carried out within the previous year, unless the appliances have been installed for less than 12 months.
- Retention: keep the record until two further checks have been done, which may be longer than two years. For an appliance or flue removed from the property, keep it for two years from the date of the last check.
- The copy given to a new tenant need not carry the engineer's signature, so long as it states that a signed copy can be inspected on request, and where the tenant's rooms contain no gas appliance the record may be displayed prominently instead of handed over.
- The 10 to 12 month window: since 2018 the check can be carried out any time from 10 months after the last one while keeping the original deadline date, so booking early costs nothing in renewal date and leaves room for one failed appointment.
Is a gas safety check the same as a boiler service?
No, and HSE says so directly: do not assume an annual service inspection includes the points a safety check requires, and do not assume a safety check on its own provides effective maintenance. The check answers whether the appliance is safe to use today. A service is maintenance to the manufacturer's instructions, with the appliance opened, cleaned and adjusted. A landlord carries both duties, the annual check under regulation 36 and a continuing duty to keep appliances and flues maintained in a safe condition, and most people book the two on one visit because the engineer is already there with the case off.
How does the record reach the landlord?
That depends entirely on how the engineer does their paperwork, and it is the part of the job a landlord actually experiences. A paper record gets posted or scanned when the engineer next sits down, which can be days after the visit and eats into the 28 days. Engineers using Manifold fill the record in on their phone at the appliance and send it as soon as the last reading is in, so the landlord's copy lands while the van is still outside and the tenant's copy goes out the same day.
Only a Gas Safe registered engineer can carry out this check and judge whether an appliance is safe. This guide explains what the law requires and what a check usually covers, and the engineer's assessment at the property is what counts. The regulations quoted here are current at the date above, so check legislation.gov.uk and HSE before relying on them.
Frequently asked
Sources
- legislation.gov.uk, Gas Safety (Installation and Use) Regulations 1998, regulation 26 (the 26(9) examinations)
- legislation.gov.uk, Gas Safety (Installation and Use) Regulations 1998, regulation 36 (landlords' duties, record contents, 28 days, retention)
- HSE, Safety in the installation and use of gas systems and appliances: ACOP and guidance L56 (Appendix 3, and the guidance on regulations 9, 26, 30 and 36)
- HSE, gas safety check records and what to keep
- HSE, maintenance of gas appliances and flues (installation pipework and the annual check)
- HSE, gas safety checks: what needs them
- HSE, gas safety for landlords and letting agents
- HSE, Landlords: a guide to landlords' duties, INDG285(rev3)
- HSE, Gas appliances: get them checked, keep them safe, INDG238(rev3)
- Gas Safe Register, Gas Industry Unsafe Situations Procedure explained (factsheet, 22 April 2024)
- IGEM/G/11 Edition 2, Gas Industry Unsafe Situations Procedure, as published by Gas Safe Register
- GOV.UK, Smoke and Carbon Monoxide Alarm (Amendment) Regulations 2022: guidance for landlords and tenants
- Gas Safe Register
Related guides
Last reviewed September 2026. This guide is general information, not legal or safety advice, gas safety work must be carried out by an appropriately Gas Safe registered engineer. Rules can change, so check the linked official sources for the current position.