Health and Safety
Executive / Commission
Contract Research Reports
Results of full-scale experiments are reported to determine the
effect of extract fans on open flued
gas appliances. Three types of gas appliance (a gas fire, a central
heating boiler, and a combi boiler)
and two type of extractor (window mounted, and cooker hood) were
used. Two different ventilator
heights were also used. Tests were carried out with different
extract rates, and with both initially cold and hot flues. The
extraction rate was increased until a reversed flow in the flue
could be maintained. Temperatures in the room containing the
appliance were measured. Concentrations of carbon monoxide, carbon
dioxide and oxygen were monitored at several heights in different
rooms of the experimental house facility, and also close to the
boiler, and in the air extract system. During the final part of the
test the ventilator was gradually opened from the minimum size
recommended by the appropriate British Standard until the flue
pulled normally.
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