Safety Alert: Gas boilers - flues in voids

Note: This Alert has been superseded by the safety notice dated 2 December 2010

2 October 2008

Who should read this alert?

• Property owners, landlords and tenants living in, or responsible for, properties with gas central heating appliances (boilers) that are located on internal walls. These types of boilers may have a flue that runs through the ceiling void (the space between the ceiling and floor of the room above); within a purpose built enclosure/duct or even through another property.
• Builders, property developers, managing agents and gas engineers.
• If your boiler is located on or near an external wall (where the flue goes straight out through the wall or goes vertically out through the roof), you do not need to read any further.

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Why is this alert being issued?

• To raise awareness of the potential dangers from certain types of flues connected to gas-fired central heating installations in some properties.
• HSE has become aware that some of these flues may not have been installed properly, or may have fallen into disrepair without anyone noticing.
• If the flue is not in good condition, this can affect the performance of the boiler. If the boiler is not working efficiently it may start to produce high levels of harmful carbon monoxide (CO) gas.
• CO may then enter the ceiling void/enclosure through any breaks in the flue (eg where joints are not sealed properly or where the flue material has degraded over time). It could then enter the living spaces above and below the flue.

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What is carbon monoxide (CO) and why is it so dangerous?

CO is a poisonous gas produced by incomplete burning of carbon-based fuels such as gas, oil or solid fuel. You can't see it, taste it or smell it, but it can kill and injure quickly, and without warning.

Further information on carbon monoxide (CO)

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What is the problem?

• If the flue that takes the waste products from your gas boiler to outside has a break in it, and your boiler is not operating correctly then CO could enter your property.
• In some properties the flue can be hidden, built-in, out of sight, or in a void such as the ceiling. In such cases it can be difficult to see whether the flue has been installed correctly, or whether it is still in good condition when the appliance is serviced.

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Should I be concerned?

• Data indicates that this problem is restricted to the flues to boilers that are located away from external walls. The flue to this type of boiler is more likely to be run through a void, such as the ceiling void.
• This type of installation is most common in multi-storey flats and apartments built since 2000; some modern terraced homes could also be affected.
• Older properties that have recently been renovated or modernised may also have gas boilers located away from an external wall with the flue running through the ceiling void or other enclosure.
• It appears that in some properties where the flue runs through the ceiling void or other concealed route there is no means for the flue to be visually checked (eg when the appliance connected to the flue is being serviced or maintained). This alert is relevant to such cases.
• Just because the flue may run through a ceiling void doesn't mean that you're at risk. It's when the flue was not properly installed or has been damaged that there may be a problem. One indication that a flue running through a ceiling is damaged can be staining on the ceiling. This is caused by condensation leaking out of the flue. If you've had to redecorate the ceiling due to staining, and the cause was not identified, then it might have been due to a break in the flue. Staining of building material around the flue can be another sign of flue damage.
• If you regularly (every 12 months) have your gas appliance checked for safety by a registered engineer then they should have picked up any concerns.

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What should I do if I think I'm at risk?

• Contact your builder and/or a Registered Gas engineer about this alert (they should be able to offer further information and help in getting problems resolved). You should be able to find the name of the builder in the legal documents you received when you bought the property, even if you bought it from a previous occupant.
• If you live in rented accommodation then bring this alert to the attention of your landlord or managing agent.
• As a property owner, if you've not had your gas boiler and flue checked in the last 12 months then arrange a service visit by a Gas Safe registered engineer.
• Fit a audible CO alarm - HSE strongly recommend these to anyone with a gas appliance in their property; arrange for a CO alarm to be installed if you do not already have one. Please note that CO alarms do not replace the need for regular maintenance of your gas appliance by a competent registered gas engineer.
• If you have immediate safety concerns, or think you are suffering the symptoms of CO poisoning, stop using the appliance and contact the National Gas Emergency Service on 0800 111 999.
• Please do NOT attempt to check the flue system yourself. You are likely to do more harm to the installation and place you and your family at greater risk.
• Please do NOT try to install inspection hatches yourself. You may damage other key functions of the ceiling, such as fire and noise proofing.

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Further information

• Contacting your builder/property developer
  If you are unsure who your builder is, contact your home warranty provider who may be able to direct you. The largest warranty providers for new homes is the National House-Building Council (NHBC) ,(Customer Services: 0844 633 1000). Other warranty providers include Zurich and Premier. Your warranty documents will identify the provider.
  
• Contacting a Gas Safe registered gas engineer
  To find a competent engineer in your area, visit the Gas Safe Register website.

When you moved into your property you may have been given the Installation Commissioning and Service Record Log Book for your gas boiler. This should provide details of when your boiler was last serviced. It should also give details of the company that installed the system.

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Additional information for builders/property developers

Key actions needed

Specific guidance on flues in ceiling voids is contained in CORGI Technical Bulletin 200, first published in June 2007, Room-sealed fanned draught systems concealed within voids (TB200). It includes specific mention of the need to install means of access to the flue at strategic locations to allow for visual inspection. In line with this: 

• Existing properties should be checked by a registered gas engineer, as a minimum along the lines suggested by TB200. Depending on how many properties you need to check (eg some major builders/developers may have several thousand), you may wish to first work on a sample basis, selecting a number of properties to check. You should ensure that you check enough properties to give a reasonable picture of how well flues have been installed across the stock you have built. It may then be possible to reassess your sampling strategy.
• Some existing properties may require remedial works to their flues and gas appliances.
• Properties yet to be sold or under construction may require remedial works to ensure their gas appliances and flues are safe, and to install adequate means of access to enable inspection of the flue route. Those in control of the construction process should ensure that the requirements of TB200 will be met and that the flues are properly installed.
• The design of properties still on the drawing board will need to be checked to ensure the requirements of TB200 will be met.

Information to consider

When checking properties you may consider prioritising:

• Properties where you have received previous complaints from residents about the gas appliances or staining to ceilings or adjacent surfaces;
• Developments where no recent maintenance is likely to have taken place (if these can be identified).

Background

Construction processes may vary between developments, so it is possible that some appliances and flues were commissioned before the ceilings were installed. Some ceilings may also be of a removable tile design, allowing easy access. However, this is less common in residential properties. Certainly, before TB200, gas engineers should have been aware of the need to visually inspect the flue during appliance commissioning and at service/maintenance visits although enquiries indicate awareness of this issue has not been high across the construction and gas industries.

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Additional information for gas engineers

Legal requirements

The Gas Safety (Installation and Use) Regulations 1998 (GSIUR) require flues to be suitable for the appliance concerned and to be in proper condition for the safe operation of the appliance. After installation and before the gas appliance it serves can be brought into use, the effectiveness of the flue should be examined.

The installation of a gas appliance to a flue that is not suitable and in proper condition is a breach of GSIUR by an engineer.

Existing industry guidance

Specific guidance on flues in ceiling voids is contained in a CORGI Technical Bulletin, first published in June 2007 Room-sealed fanned draught systems concealed within voids (TB200). It includes specific mention of the need to install means of access to the flue at strategic locations to allow for visual inspection. This is now also a requirement of BS 5440-1: 2008.

If you are a gas engineer or builder/property developer undertaking work in premises where this issue may be relevant you should ensure you have a full and up to date knowledge of the industry guidance outlined in CORGI's Technical Bulletin TB200 "Room-sealed fanned draught flue systems concealed within voids".

As well as covering the initial installation of flues in ceiling voids, TB200 gives advice on maintenance and inspection of existing installations where there is no access to the ceiling space or enclosure.  It directs gas engineers to undertake a thorough assessment of the risk, and outlines a series of factors they should consider (eg evidence such as stains in the ceiling/enclosure area that could indicate leakage from the flue). Based on this risk assessment you should form an opinion on whether the gas appliance is safe to continue in use, and what action to recommend to the homeowner, or landlord and tenant.

Before TB200, gas engineers should have been aware of the need to visually inspect the flue during appliance commissioning.  Construction processes may vary between developments, so it is possible that some appliances and flues were commissioned before the ceilings were installed. Some ceilings may also be of a removable tile design, allowing easy access.  However, this is less common in residential properties.

Important note

It is clear that the need to install means of access to flues in ceiling voids/enclosures was neglected in some properties constructed after TB200 was published. Increasingly, it appears that awareness of the requirements of TB200 and the need for inspection points amongst engineers and developers is not as widespread in the industry as HSE would have expected.

If you receive a request from a homeowner/tenant/landlord in relation to this issue ensure as a minimum you undertake the checks required by TB200. However, please note that you may also have other information which should include in your risk assessment to identify the required actions needed specific to that property.

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