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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