The essentials in 30 seconds
HSE advises that gas appliances, boilers included, are serviced at least once a year by a Gas Safe registered engineer, or as the manufacturer's instructions say. By law, anyone who works on a gas appliance must examine the flue, the supply of combustion air, the operating pressure or heat input (or combustion performance) and its safe functioning. Landlords have a separate legal duty: an annual gas safety check on every gas appliance and flue they provide, a record kept for at least two years, a copy to existing tenants within 28 days and to new tenants before they move in. Before anyone touches your boiler, ask for their Gas Safe ID card and check the back lists the work they are doing.
- Yellow or orange flames, soot or brown staining, a pilot light that keeps going out and extra condensation on windows are HSE's warning signs.
- A CO alarm to EN 50291 is an early warning; it adds to servicing rather than replacing it.
- The annual safety check leaves out installation pipework, so ask for a tightness test if you want it covered.
Why a boiler should be serviced every year
A gas boiler burns fuel next to your living space, and it stays safe only while it burns cleanly and its flue carries the exhaust outside. When combustion goes wrong, the boiler can produce carbon monoxide, a gas you cannot see or smell. HSE's advice for homes is simple: have gas appliances regularly maintained and serviced at least annually by a Gas Safe registered engineer. For appliances in rented homes, HSE says they should be serviced in line with the manufacturer's instructions, or every year where those instructions are missing, unless a Gas Safe engineer advises otherwise.
A service also gives you:
- A written record of what was checked, useful for your warranty, a house sale or an insurance claim.
- An early look at wear, so a part can be replaced in autumn rather than on the coldest night of the year.
- A chance to ask questions about pressure drops, noises or error codes you have noticed.
This guide covers gas and LPG boilers. In the US a home is more often heated by a furnace; see our furnace maintenance guide. For an oil boiler, book a technician qualified for oil appliances, as the Gas Safe Register covers gas work only.
What is included in a boiler service
The Gas Safety (Installation and Use) Regulations 1998 set a legal minimum: anyone who carries out work on a gas appliance must immediately examine four things (regulation 26(9)). On top of that, the engineer follows the manufacturer's service schedule for your model.
| Area | What the engineer looks at | Why it matters |
|---|---|---|
| Flue | That the flue is effective: intact, sealed and discharging outside, with the terminal clear | A faulty flue can let combustion gases into the home |
| Combustion air | That the boiler gets the air supply it needs | Starved combustion can produce carbon monoxide |
| Pressure, heat input or combustion | The operating pressure or heat input, or a combustion performance check where those are impractical | Shows whether the gas is burning as designed |
| Safe functioning | That the boiler operates safely, including its safety devices | Confirms it shuts down when it should |
| Condition | Signs of deterioration in the appliance, ventilation and flue | HSE's minimum for maintenance where no manufacturer instructions exist |
| Manufacturer's checklist | The model-specific items in the installation and service manual | Parts and intervals vary between boilers |
Ask the engineer to talk you through the results and give you a written record. If they find a defect, they should explain whether the boiler is safe to keep using.
Things you can check between services
- The pressure gauge on a sealed system: compare the cold reading with the range in your manual. If it keeps dropping, see boiler pressure and bleeding radiators.
- The flue terminal outside: keep plants, bins and stored items clear of it.
- Radiators cold at the top: bleed them as our radiator guide shows.
- The CO alarm: press the test button once a month.
Boiler service vs gas safety check
The two are often booked together, but HSE treats them as separate duties.
| Boiler service | Gas safety check | |
|---|---|---|
| Purpose | Maintenance: keeping the boiler working safely and efficiently | Safety: confirming each appliance and flue is safe to use |
| Who needs it | Everyone with a gas boiler (HSE advice) | Landlords, by law, for appliances and flues they provide |
| How often | At least yearly, or as the manufacturer says | Every 12 months |
| Paperwork | A service record, as the engineer provides | A gas safety record with set contents, kept for at least two years |
| Pipework | Ask for a tightness test if you want it | Installation pipework is outside the check |
HSE notes that the annual gas safety check does not cover installation pipework, and recommends asking the engineer to test the whole gas system for soundness and visually examine the pipework as far as practicable.
How to check your engineer is on the Gas Safe Register
The Gas Safe Register is the official register of gas businesses and engineers for piped natural gas and LPG in Great Britain, Northern Ireland, the Isle of Man and Guernsey. Under the 1998 regulations, a business doing gas work must be on it.
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01
Ask for the ID card
Every registered engineer carries a Gas Safe Register ID card with a photograph, a registration number and an expiry date.
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Read the back
The back lists the categories of gas work the engineer is qualified for. Check that it covers the boiler or appliance they are working on.
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Check the register
Look the engineer or business up with the Find an Engineer service on the Gas Safe Register website, or call the helpline on 0800 408 5500.
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Or send a text
HSE says you can text "Gas" followed by the engineer's seven-digit licence number to 85080.
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Keep the paperwork
Ask for a written record of the service and keep it with your boiler manual.
Landlord gas safety check: the legal duty
For rented homes, the duty comes from regulation 36 of the Gas Safety (Installation and Use) Regulations 1998, enforced by HSE across Great Britain. These are the points HSE sets out:
- Every year: make sure a gas safety check is done on each gas appliance and flue you own and provide, whether fixed or portable.
- Before a new lease: the checks must have been done within the year before the lease starts.
- Keep records: for at least two years. If you use the option to check up to two months early, keep each record until two further checks have been done.
- Give copies: to existing tenants within 28 days of the check, and to new tenants before they move in.
- Fix defects promptly: take action on any defect shown on the record.
- Maintain as well: maintenance is a separate duty from the safety check, and all maintenance and repairs must be done by a Gas Safe registered engineer.
Since the 2018 amendments, a landlord can have the annual check done up to two months before it is due and keep the original deadline, so the yearly date does not creep earlier. A new appliance can be brought into line with the others once, by extending its first check by up to two months.
| Item | Details |
|---|---|
| Each appliance or flue | A description and its location |
| The engineer | Name, registration number and signature |
| Dates | The date each appliance or flue was checked |
| Addresses | The property address, and the landlord's or agent's name and address |
| Results | Any safety defect found and any remedial action taken |
| Scope | Confirmation that the regulation 26(9) checks were carried out |
Landlords in England also have duties on CO alarms in rooms with fixed combustion appliances; our CO alarm guide summarises them.
Signs your boiler needs an engineer before its service date
| What you notice | What it can mean | What to do |
|---|---|---|
| Yellow or orange flames where they used to be blue | Gas burning incompletely | Stop using the appliance and call a Gas Safe engineer |
| Soot or yellow-brown staining on or around the boiler | Poor combustion or flue problems | Stop using it and call an engineer |
| A pilot light that keeps blowing out (older boilers) | One of HSE's signs of an unsafe appliance | Stop using it and call an engineer |
| More condensation than usual on the inside of windows | Possible CO warning sign, as HSE lists it | Check your CO alarm and book an engineer |
| Pressure that keeps falling | A leak, a relief valve or an expansion vessel issue | See our pressure guide; call an engineer if it drops every few days |
| Radiators cold at the top | Air in the system | Bleed the radiators and top up the pressure |
| Repeated error codes or lockouts | A fault the boiler has detected | Note the code from the display and the manual and book a visit |
Carbon monoxide alarms and symptoms
HSE strongly recommends carbon monoxide alarms as an early warning, while stressing that they never replace regular servicing and safety checks. Choose an alarm that complies with British Standard EN 50291 and carries a British or European approval mark such as a Kitemark.
HSE notes that early CO symptoms are easily mistaken for food poisoning, a viral infection, flu or simple tiredness. Its list includes headaches or dizziness, breathlessness, nausea, tiredness, chest or stomach pains, erratic behaviour, visual problems and loss of consciousness. If you think you have been exposed, get into fresh air and seek urgent medical advice from your GP or A&E.
How to prepare for a boiler service
- Clear the cupboard around the boiler and make the flue terminal outside easy to reach.
- Note any error codes, noises, pressure readings or cold radiators since the last visit.
- Have the boiler manual and the previous service record ready.
- Book in late summer or early autumn, before the heating season.
- Ask for a written record, and for a gas tightness test if you want the pipework covered.
Boiler service: frequently asked questions
How often should a boiler be serviced?
At least once a year by a Gas Safe registered engineer, as HSE advises, or more often if the manufacturer's instructions say so.
What is included in a boiler service?
At minimum the engineer examines the flue, the combustion air supply, the operating pressure or heat input (or combustion performance) and safe functioning, then follows the manufacturer's service checklist.
Is a boiler service a legal requirement?
For landlords, an annual gas safety check on each appliance and flue they provide is a legal duty. For homeowners, HSE advises a yearly service.
Is a boiler service the same as a gas safety check?
No. The service is maintenance; the gas safety check confirms each appliance and flue is safe and produces a record. Many people book both together.
How do I check an engineer is Gas Safe registered?
Ask for their ID card and read the back for the work categories, then check the Gas Safe Register website or call 0800 408 5500.
How long must landlords keep gas safety records?
At least two years, and longer if the check was done early under the two-month flexibility.
When must tenants get a copy of the gas safety record?
Within 28 days of the check for existing tenants, and before they move in for new tenants.
Why is my boiler flame yellow?
A yellow or orange flame can mean the gas is burning incompletely, a warning sign for carbon monoxide. Stop using it and call a Gas Safe engineer.
Sources
UK health and safety guidance and legislation, checked on 27 October 2026.
- HSE · Domestic gas safety FAQs ↗Annual servicing, ID cards and work categories, checking by phone, website or text, warning signs of unsafe appliances, CO symptoms, EN 50291 alarms and the gas emergency number.
- HSE · Gas Safe Register ↗What the register covers, the legal duty to be registered and what the ID card shows.
- HSE · Landlords: gas safety checks, who needs them ↗Regulation 36(1), the yearly check on each appliance and flue, and checks before a new lease.
- HSE · Landlords: gas safety check records ↗Keeping records for two years, copies within 28 days and before move-in, and the contents of the record.
- HSE · Landlords: maintaining gas appliances and flues ↗Servicing to manufacturer's instructions or annually, the difference between maintenance and safety checks, and pipework outside the annual check.
- legislation.gov.uk · Gas Safety (Installation and Use) Regulations 1998, regulation 26 ↗The four checks required whenever someone works on a gas appliance.
Service due?
Note any error codes and pressure readings, clear access to the boiler and ask to see the engineer's Gas Safe ID card when they arrive.