Gas boilers - flues in voids
(Update to HSE safety alert issued 2nd October 2008)
This Safety Notice provides updated information to that in the safety alert that was issued by the Health and Safety Executive (HSE) on 2nd October 2008 following a death earlier that year.
The purpose of the original Alert was to raise awareness of the potential dangers from certain types of flues connected to gas-fired central heating installations in some properties (particularly, but not exclusively, a large number of flats and apartments completed since about 2000) that may not have been installed properly, or may have fallen into disrepair.
Where boilers are located away from external walls, flues are more likely to run through ceiling (or wall) voids. In such cases when the gas appliance is serviced or maintained it can be difficult, or impossible, to determine whether the flue has been installed correctly or whether it is still in good condition.
Where a flue fault exists in combination with a boiler which is not operating correctly, dangerous levels of carbon monoxide (CO) could be released into the living accommodation. CO is a colourless, odourless, tasteless, poisonous gas produced by incomplete burning of carbon-based fuels. It stops the blood from bringing oxygen to cells, tissues, and organs and can kill quickly, without warning.
The 2008 Alert referred to the relevant gas industry technical guidance which gas engineers were expected to follow. A revised version of this guidance has now been published by Gas Safe Register. This changes the approach that Gas Safe registered engineers  will take when they encounter relevant installations.
The purpose of this Safety Notice is to make homeowners, landlords and tenants aware of these changes as action might be required. It is not, however, the only means of communication. An industry working group (including representatives of the gas industry, home builders, home warranty providers and boiler manufacturers, assisted by HSE) will ensure that information is readily available to all those who may be affected.
The introduction of fan-flued gas appliances in the mid 1990s allowed gas central heating boilers to be installed away from external walls. This meant that builders could design new-build and refurbishment properties with boilers being installed on internal walls to make better use of the available space. The flues to these boilers were, in some cases, routed through voids in the ceiling space (and through stud walls) between properties above.
This practice became progressively more popular from 2000 onwards and the vast majority of affected systems are thought to be located in new build flats and apartments completed since 2000. It is however possible that other types of home may have similar central heating systems installed.
Gas engineers are legally required to check the flue after carrying out any work on the boiler. This will include a visual inspection. Similarly, when an engineer installs a boiler they need to ensure that it can be used without constituting a danger to anyone; this would include checking whether the flue is safe. The original installer and every subsequent servicing or maintenance engineer need to be able to check that:
- the flue is continuous throughout its length;
- all joints are correctly assembled and are appropriately sealed
- the flue is adequately supported throughout its length.
Unless the gas engineer can make these checks they cannot ensure that the flue from the boiler is safe in order to comply with their legal duties. This necessitates the provision of appropriate inspection hatches in the ceiling (and, where relevant, stud wall).
The original industry technical guidance (aimed at registered gas engineers) advised that where the flue to the boiler was concealed within a void and could not be visually inspected it should be assessed as "not to current standards" (NCS) in accordance with the Gas Industry Unsafe Situations Procedure. This was dependent on there being no other risks being present which may have made the boiler unsafe.
Revised guidance takes effect on 1st January 2011. This is the result of the industry working group who undertook a review of the original guidance and concluded that the potential risk from such systems, should it not be possible to inspect the flue, requires an alternative approach to ensure that the necessary remedial action is taken.
The revised technical guidance requires inspection hatches to be fitted in properties where the flue is concealed within voids and cannot be inspected. The homeowner (or landlord etc.) has until 31st December 2012 to arrange for inspection hatches to be installed. Any gas engineer working on affected systems after 1st January 2013 will advise the homeowner that the system is "at risk" (AR) in accordance with the GIUSP and, with the owner's permission will turn off the gas supply to the boiler so it cannot be used.
In the interim period, where no inspection hatches are fitted, the registered gas engineers will carry out a simple risk assessment which should ensure that the risk from exposure to CO is managed in the short-term. This risk assessment includes:
- looking for signs of leakage along the flue route
- carrying out a flue combustion analysis check (and obtaining a satisfactory result)
- checking for the presence of suitable audible carbon monoxide (CO) alarms (and installing such alarms where they are not already fitted).
As long as this boiler passes the series of safety checks and the risk assessment does not identify any concerns about its safety, it can be left on. Suitable inspection hatches will however need to be fitted to the ceiling (or wall, as appropriate) by end 31st December 2012. Wherever possible it is recommended that inspection hatches are fitted before this date.
Once inspection hatches have been fitted, the gas engineer will be able to make sure that the flue is safe and was installed in line with the relevant standards and manufacturers instructions.
A simple explanation of the issue, the risks and how the matter can be resolved, as well as a number of frequently asked questions, have been developed for householders by gas safe register, a copy can be found here.
- Attempt to check the flue system yourself (unless you are a Gas Safe registered engineer). You are likely to do more harm to the installation and place you and your family at greater risk.
- Try to install inspection hatches yourself. You may damage other key functions of the ceiling, such as fire and noise proofing. If you live in rented accommodation and think your property might be affected:
Bring this Notice to the attention of your landlord or managing agent. It is the responsibility of the landlord to ensure that inspection hatches are installed and that the boiler and flue are checked every year.
If you think you are suffering the symptoms of CO poisoning:
Turn the appliance off immediately and contact the National Gas Emergency Service on 0800 111 999