Chimneys


Even efficient stoves and boilers will produce some unburnt volatiles particularly when slumbering or damped down. If these gases cool down in the chimney they will condense and form tar deposits creating a fire risk and impeding air flow. This can be prevented by using an insulated flue so that the gases remain hot until they reach the atmosphere. Insulation also protects the building in the event of a chimney fire.

Chimneys need to be swept at least once a year in order to avoid the risk of a chimney fire and carbon monoxide poisoning. As with the burning of any fuel for the production of heat, wood can produce this poisonous carbon monoxide if the flue or chimney is blocked, the equipment is faulty or there is a lack of ventilation. A list of chimney sweeps is available from the National Association of Chimney Sweeps.

Building regulations (Part J) provide guidance on good flue design. Key recommendations include:

• Once the flue has left the appliance it should remain within 30 degrees of vertical
• There must be provision for sweeping the flue
• Only one appliance should enter the flue.
• The flue should be insulated to prevent condensation of tar and water and to protect the building.

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