Insufficient air (air starvation) An open fire requires a free supply of air for two purposes. Primary air which allows for combustion, and Secondary air, which carries the smoke away up the chimney. Primary air demand is usually small and is often supplied below the bed of the fire (as in a BAXI grate through a small diameter pipe). Secondary air demand is much greater and it is this that prevents the smoke spilling out of the fireplace. If your floors are solid concrete, and the windows and doors are new (and are fitted with draught strips), then there may be no route for an adequate volume of air to come into the room. To test for air starvation: Take a piece of Kleenex tissue paper. Tear it into strips approx. 25mm (1") wide by approx. 150mm (6") long and separate to a single ply. Tape one or more strips to the top of the fireplace. Note what happens when doors and windows are opened and closed. If the strips hang languidly when all are shut and pull back into the room when the door is pulled open, you might be suffering from air starvation. If so, contact the experts.

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