Flues In Voids (FIV)

Readers may or may not be aware of the problems of flues in voids (FIV). For those of you who are not up to date with this issue I will try to clarify things.


When balanced flue boilers were first introduced they had to be fitted on an outside wall to enable the flue and combined air intake to be fitted through the wall, whilst this was an advance from traditional open flued boilers which needed a flue (chimney) up through the roof it sometimes made siting the boiler difficult. As technology progressed, fan flued boilers became the norm and some manufacturers developed flue systems which could be longer in length, meaning the boiler did not need to be fitted on an outside wall. In some instances flues can be as long as 45m. Many blocks of apartments were built with boilers situated away from an outside wall and the flues routed through the same and neighbouring apartments to the outside. Most of these flues are enclosed in boxing and/or floor voids for aesthetic reasons.

What is the problem?

When flues are enclosed, there is no way of checking if the joints in the sections of flues are correctly assembled and free from defects at a later date. If a flue joint fails, products of combustion (POCs) can escape into the building. One of the POCs produced by any fossil fuel burning appliance is Carbon Monoxide which can cause severe illness or death.

What is being done about it?

The gas industry has produced a document (TB008) which details the steps to be taken by registered gas installers (RGIs) when encountering FIV. The RGI will undertake a risk assessment and decide on a course of action. Whatever the outcome you will have to have inspection hatches fitted to enable inspection of every joint in the flue system; this work will need to be carried out by 31st December 2012. If this work has not been carried out by this date any RGI carrying out work at your property will have to switch off your boiler for your own safety.

What should I do now?

If you are in any doubt about your flue system, contact a Gas Safe Registered Engineer to check your system. For further information go to http://www.gassaferegister.co.uk/advice/flues_in_voids.aspx