Photograph 1: Typical flue within a ceiling void
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; and
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
(GIUSP - see Reference section for explanation). 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; and
carrying out a flue combustion analysis check (and obtaining a satisfactory result); and
checking for the presence of suitable audible carbon monoxide (CO) alarms (and
installing such alarms where they are not already fitted).