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Technical back to basics
Back to basics: flues in voids
Guidance and frequently asked questions for gas engineers working on concealed room-sealed fanned-draught chimney/ flue systems (flues in voids) in their customers’ homes.
Whenever you carry out work on a flued appliance, GSIUR 26(9) requires that you immediately examine and confirm the effectiveness of the flue. But this requirement is particularly difficult where there is a concealed chimney/flue system, particularly those in ceiling voids.
Technical Bulletin 008 was developed by an industry-wide working group to provide guidance for these situations. It makes clear that any concealed room-sealed fan-draught boiler chimney/flue system installation being worked on where you cannot confirm the effectiveness of the chimney/flue system should be classified as At Risk and, with the responsible person’s permission, it should be turned off in accordance with the Unsafe Situations Procedure (IGEM/G/11).
If your customers refuse permission, you should ask them to sign paperwork to confirm that they accept responsibility for a situation which could result in a serious incident. In the case of an Immediately Dangerous situation, where permission to disconnect the boiler has not been given, you should contact the Gas Emergency Contact Centre.
What does the guidance cover – and what is excluded?
The guidance mainly covers situations where the chimney/flue system passes through ceiling voids, floor voids or behind false walls.
It does not apply to chimney/ flue systems incorporating: • Vertical condensing flexible
room-sealed fanned-draught chimney/flues systems installed in enclosures, such as constructional chimneys etc, which are sealed so that any leakage of products of combustion cannot pass from the enclosure to any room or internal space; and • Short chimney/flue systems such as those that are connected directly from an appliance to outside air through an external wall.
Nor does it apply to the air inlet pipes of twin-pipe chimney/ flue systems.
How to deal with it
The Technical Bulletin contains guidance on how to deal with an existing concealed room-sealed fanned draught boiler chimney/ flue system in order of preference:
• Fit inspections hatches, CO alarms and regular servicing and maintenance
Inspection hatches at appropriate locations are the most effective way to examine the integrity of the chimney/flue system when the flue has been concealed within the fabric of the building. This may be boxing or ceiling voids containing a flue or where the flue has been installed in a concealed location, for example boxing-in or a ceiling void.
Inspection hatches should allow the overall integrity of chimney/flue system to be confirmed. You need to consider any other defects before you can determine whether it is safe. If you can confirm that it is complete/ intact and effective, then provided that any identified installation defect(s) do not constitute an increased risk of chimney/flue system failure, it is safe for continued use. Typical installation defects that may contribute to an increased risk of chimney/flue system failure include: – For condensing boilers, inadequate gradient/fall of the chimney/flue system back to the boiler, which may trap condensate, putting excessive strain on the chimney/flue system joints or supports – Incorrect/inadequate chimney/ flue system support, constituting significant risk of chimney/flue system failure – Signs of condensate/water leakage at chimney/flue
system joints – Incorrect flue material/joints other than specified by the appliance manufacturer, etc.
Following the guidance given in Technical Bulletin 008 (Edition 3) is not compulsory and you may take other action. But following the guidance will ensure that you are complying with the regulations, and the relevant enforcing authorities may refer to this guidance as industry practice.
Chris Riley from Sound Installations in Ware, Hertfordshire had been asked to replace a boiler. There were no inspection hatches along the plastered-over boxing for the chimney/flue. When he removed the boxing, he found that the chimney/flue had been installed using soil pipe, metal flue outlet pipe, along with a chimney from a different manufacturer than had supplied the boiler. The joints were taped together with duct tape, there was no fall on the chimney/flue back to the boiler and there wasn’t a clip in sight.
• Fit a CO void monitoring safety shut-off system (COSSVM) and regular servicing and maintenance
In exceptional circumstances, the installation of inspection hatches may not always offer the best, nor a practical option – for example, if the enclosure around the chimney/flue is too small to allow effective examination of the whole chimney/flue system, or where fitting inspection hatches could affect any existing fire protection measures.
Back to basics: flues in voids
Systems that monitor a void for the presence of CO and which, on activation, shut down the faulty boiler, may be considered as a method of providing an additional level of protection for property occupiers who do not have, nor agree to have inspection hatches installed.
This form of protection, along with the 26(9) checks as a minimum will ensure, as far as is reasonably practicable, that the boiler and chimney/flue system are safe for continued use.
Note: These systems are not acceptable as a substitute for inspection hatches for new or replacement installations, which will need to meet the requirements of relevant Building Regulations and standards. Your customer should understand that when their boiler needs replacing, ceiling hatches will need to be fitted at the same time as the pressure and/or the heat input (gas rate), you must verify the following: • That the combustion performance of the appliance is correct in all modes of operation eg, in both high and low fire rates, and complies with the manufacturer’s instructions or
BS 7967 • Where manufacturers provide an air inlet sampling point, that any specified O2 levels are in accordance with the manufacturer’s instructions • Plume/heat discharge is evident from the chimney/flue termination with the boiler in operation • There is no evidence of distress on the enclosure or ceiling along the complete length of the chimney/flue system • There are no known previous issues relating to the property, or other properties in the same development, that could be
related to concealed chimney/ flue systems issues that have not been corrected/rectified before. You should enquire with the responsible person.
Exception
A short chimney/flue system concealed in a void may be acceptable – such as vertical chimney/flue system passing through a flat or pitched roof extension, or similar, with no means of access to allow inspection – when the following can be confirmed (see illustration): • There are no changes in chimney/flue direction • There are no signs of distress likely to indicate a chimney/flue issue exists, and • The chimney/flue length does not exceed the maximum single chimney/flue system component length supplied by the manufacturer, or • Documented confirmation from the installation business stating that there are no chimney/flue joints in the concealment; the installation can be considered acceptable.
You should record these criteria on your job documentation and give a copy to your customer.
RIDDOR reporting
Immediately Dangerous situations relating to these types of chimney system should be reported under RIDDOR 11(2) .
Adjacent property
You may find chimney/flue systems routed through an adjacent property, even though this installation practice is no longer permitted. In these situations, and if checks of the boiler and the chimney/flue system in the property containing the boiler are all satisfactory, you should take reasonable steps to ensure overall chimney/flue system integrity. Reasonable steps may include: • Making enquires with all parties and asking to see evidence of reports of examinations made by them, or on their behalf. • Making enquiries with the occupants of adjacent properties in order to gain access • Leaving documentation with the occupier(s) of adjacent property, explaining the requirement and seeking arrangements for access. Make sure you record the steps you have taken.
If you can’t gain access to an adjacent property and there is no evidence that there are any chimney/flueing issues, you can leave the boiler and chimney/flue system operational.
However, if you suspect a problem, you should check the complete length of the chimney/flue system (including parts of the chimney/flue system routed through adjacent property). Until you can gain access to the adjacent property, you should classify the installation as At Risk.
complete chimney/flue system is replaced. A void monitoring system (COSSVM) alone will not satisfy the requirements of the Building Regulations/Standards. Where neither of these situations exists, you should continue to undertake regular service/ maintenance on the boiler, recommend the installation of CO alarms, and classify the installation as At Risk in accordance with IGEM/G/11.
Boiler operational safety and other checks
In addition to confirming the effectiveness of the concealed chimney/flue; the supply of combustion air, the operating This is an abridged article, covering the main points of Technical Bulletin 008. To read the full Technical Bulletin, please log in to your online account at
www.GasSafeRegister.co.uk/sign-in
Guidance for your customers is available at:
www.gassaferegister.co.uk/gas-safety/home-gas-safety/ check-your-gas-appliances/flues-in-voids-faqs/
Flues in voids:
frequently asked questions
The room-sealed fanassisted boiler chimney/flue is boxed in rather than in the ceiling void. Does it need inspection hatches?
Yes, the requirement to be able to examine the chimney/flue system in this situation is the same. It is accepted that inspection hatches of the recommended 300mm x 300mm dimensions may not always be able to be fitted due to the size, configuration and design of any boxing or ducting. Each situation should be assessed on its own circumstances.
Provided that you can examine the chimney/flue system to confirm it is complete/intact and effective, you have met the objective of the guidance. This may mean that any boxing will need to be altered so that it is removable or has removable panels. However, where it is possible to see through or down a short section of duct sufficiently to examine the chimney/flue system and confirm it is intact/ complete and effective, this will alleviate the need to alter the boxing or add removal panels.
The chimney/flue is routed through a roof-space that has no access to allow for the inspection of the chimney/ flue. Does the guidance in TB 008 (Edition 3) still apply?
Yes. The TB is relevant and guidance should be followed even though the chimney/flue system is not within a ceiling void. You still have an obligation to be able to examine the chimney/flue system.
The boiler chimney/ flue connects to a shared communal chimney/flue: will this come under the same requirement for inspection hatches?
Many existing shared or communal chimney/flue systems are designed for natural draught room-sealed appliances, eg, SE ducts and U ducts. In these situations, the guidance in TB 008 does not apply.
For more up-to-date communal chimney/flue systems (CFS) designed for room-sealed fan-assisted boilers, if the boiler uses one of these CFS systems, both the connecting chimney/flue pipe (and, where applicable, the been fabricated with an insulation material surrounding the system, making it difficult to confirm the safety and examine the chimney/ flue system.
It’s not practical and almost impossible to remove any insulation through inspection hatches to allow examination and then replace the insulation.
Here, you should use your best endeavour to risk-assess the chimney/flue system. The assessment should also include looking for signs of: • Staining or condensate (water) damage on the ceiling within the void area beneath the likely chimney/flue pipe run
• Chimney/flue pipes running out of alignment (kinked) • Evidence of staining or condensate (water) on the insulation material, etc.
If you observe any of these, you must check the complete length of the chimney/flue and rectify any deficiencies. Any associated appliance must not be used unless or until this is done.
separate air supply pipe) assembly from the boiler and the main communal chimney/flue will need to have a facility to allow inspection to ensure it is safe. Smilar obligations remain the same for the common part of the chimney/flue section, and further guidance can be found in IGEM/ UP/17.
What should I do about concealed chimney/flue systems that have been insulated?
Some chimney/flue systems installed in accordance with the manufacturer’s guidance have
What am I expected to do if called to repair or service a boiler in a property with no inspection hatches installed after the requirement to do so came into effect in 2013? Should I carry out the work and then classify the installation as At Risk or not work on the boiler and then classify it as At Risk?
Wherever possible you should carry out any requested work, ensuring that the boiler is appropriately safety checked as far as is reasonably possible. If there are no means of examining the chimney/flue system to confirm it is complete/intact and effective, assess it against the guidance in TB 008 and classify in accordance with IGEM/G/11.
The priority is to leave the boiler as safe as possible, irrespective of whether the customer gives permission for it to be turned off or not. In At Risk situations in owneroccupied properties, the decision as to whether to allow continued use of the boiler rests with the responsible person NOT you. Explain your opinion of the risk. It is recommended that you obtain a signature from the person to confirn that you have explained the risks, and that they do not want the appliance turned off. ■
