Skip to navigation menu

Concealed room-sealed boiler flues

Important advice for consumers who have flues which are concealed within ceiling spaces etc

Engineer inspecting a flue

Some properties, mainly flats and apartments, have been built with boiler flues which cannot be inspected because they are hidden behind walls or ceilings. The boiler flues that this information relates to are connected to room-sealed fan assisted boilers only. If you live in one of these homes then please read on for more information so you know what to do.

Gas Safe registered engineers need to be able to see the flue − which take fumes away from the boiler − as part of essential safety checks whenever the boiler is worked on. A flue in poor condition, combined with a room-sealed boiler that is not working properly, could put you and your family in danger from carbon monoxide poisoning, which can cause death or serious injury.

If your room-sealed boiler is situated on an outside wall, it is unlikely you have this type of flue. Alternatively, if your engineer can examine all of the flue, you will not need to take any further action in relation to this matter.

If you do have a room-sealed boiler where all, or part of, the flue cannot be seen, you, or your landlord, will need to arrange for inspection hatches to be fitted. This does not mean that your flue system is suddenly unsafe.

Room sensing carbon monoxide alarms are not an alternative to being able to see the flue and you will still need to have inspection hatches fitted so that the flue system can be checked. It is recommended that inspection hatches are fitted as soon as you are able to do so. From 1 January 2013, any Gas Safe registered engineer will classify the boiler as At Risk, this means that they will turn the boiler off, with your permission, and formally advise you not to use it until inspection hatches have been fitted in appropriate places.

Although most of the affected room-sealed boiler flue systems are relatively new (installed since 2000), the risk of faults leading to the release of carbon monoxide increases as the system gets older, especially if it is not serviced regularly. It is important that you have your gas appliances safety checked annually. .

You need to take action now

If you think the flue system serving your room sealed boiler is concealed in this way you should have it checked by a registered gas engineer who will be able to check it is safe and assess the installation and be able to provide you with advice on inspection hatches etc. If your property is less than two years old then contact your builder. If your property is between two and ten years old contact your home warranty provider, as you may be covered by them if there are defects in the flue. A list of the main home warranty providers is shown below. If your property is 10 years or older you should contact a Gas Safe registered engineer.

If you are a tenant, it is the responsibility of your landlord to ensure that the boiler is checked every year and the flue is able to be examined.

If you have any questions please see the list of Frequently Asked Questions. If you have a specific enquiry e.g. around building warranties please direct it one of the groups listed below.

For any additional enquiries not answered through these routes please send questions to: and it will be dealt with by a member of the group

To find a Gas Safe registered engineer in your area:

List of main home warranty providers:

LABC Warranty  0845 054 0505
NHBC (National House Building Council)  0844 633 1000
Premier Guarantee  08444 120 888
Zurich Building Guarantee  01252 387 535
Checkmate  020 7933 2626

This advice has been developed by the Flues in Voids cross-industry team. It is made up of representatives of Gas Safe Register, house builders, home warranty providers, registered gas engineers, appliance manufacturers (including HHIC) and others and assisted by HSE, to provide clear communication to industry and consumers around the issue of concealed flues which do not allow inspection.
What Next?

How often should I have a gas safety check?
Get your gas appliances safety checked every year by a Gas Safe registered engineer

Gas Safe registered engineers
Make sure you know how to check if your engineer is Gas Safe registered

Find a Gas Safe registered business in your area.
Advanced options | Find by name



Sign up to receive gas safety updates to help you stay safe

Free gas safety inspection

Had gas work completed in your property in the last six months? Nominate your installation for a free inspection today!

Free safety inspection

Fit a carbon monoxide alarm

An audible carbon monoxide alarm will alert you if there is carbon monoxide in your home

Where can I get an alarm?