Spillage test results from gas and oil fired boilers.

Spillage of combust ion products from open f lued combust ion appliances represents a source of indoor air pollutants which can cause danger to health. Air extract fans are installed in kitchens in order to remove moisture and cooking smells, but the room depressurisation which they create is a potential cause of spillage. A series of experiments was therefore set up to determine the fan flow rate and internal/external pressure difference at which spillage first occurred in different open flued gas and oil boilers. The effect of room air-tightness, size of air brick, air brick position, internal/external temperature difference and weather conditions were tested. It was found that domestic extract fans of standard size could cause spillage under a variety of conditions and at different room air-tightnesses. The results indicate that in order to prevent products of combustion spilling into the living space, air extract fans should not be installed if they can depressurise the room or space in which an open flued combustion appliance is installed.