Definition of flue in English:



  • 1A duct for smoke and waste gases produced by a fire, a gas heater, a power station, or other fuel-burning installation.

    • ‘In this issue Niven deals with fitting a close-coupled open vent, while David Taylor provides advice on the installation of extended flues.’
    • ‘The grate or fire basket holds the flames and can be fitted with a gas burner, while the flue or chimney extracts the smoke.’
    • ‘Main causes of fatal accidents are blocked or leaky flues, poor ventilation, poor installation and maintenance, faulty appliances, or misuse.’
    • ‘A crack in a fire flue was the most likely cause of that blaze, which ripped through the roof, dining room and wrecked a third of the castle on January 21.’
    • ‘Blocked flues and chimneys stop the gas escaping - this allows it to build up in a room where it could be breathed in.’
    • ‘Six stainless steel flues vent forge smoke through the corrugated iron roof which is cut away at the ridge for a skylight that runs the length of the studio.’
    • ‘The firm is to install flue gas desulphurisation equipment at the stations.’
    • ‘We climbed back onto our skidoos, tearing across country to a Lapp-style octagonal hut where we warmed our extremities at a roaring log fire under a central flue.’
    • ‘For the same periods, the percentage of wall, floor furnaces, and room heaters without flues has decreased from 43% to 5%.’
    • ‘If central furnace/room heaters with flues are taken as the reference group, the relative risk for wall/floor heaters, both unvented and vented, is 13.’
    • ‘British Energy is seeking Government approval to install a flue gas desulphurisation system in two generating units at Eggborough power station, near Selby.’
    • ‘Vented units are designed to be permanently located next to an outside wall, so that the flue gas vent can be installed through a ceiling or directly through the wall to the outside.’
    • ‘Do not block air vents, flues or chimneys and don't have indoor fires or stoves without proper ventilation to the outdoors.’
    • ‘Lining the flue will seal and insulate the chimney, maintaining high temperatures within the flue and preventing the smoke from condensing into soot.’
    • ‘Poor servicing or installation of appliances, inadequate ventilation or blocked flues are usually to blame.’
    • ‘The court was told that a subsequent safety check by Health and Safety officers revealed that the flue for the fire was wrongly fitted and carbon monoxide was spilling into the room.’
    • ‘A stack thermometer installed on the stove flue will give you information on gases leaving the stove.’
    • ‘Don't block air vents, flues or chimneys and don't have indoor fires in rooms without ventilation.’
    • ‘However, if the damp problem has been rectified by correct installation of the stainless-steel flue, there is no need to seal the wall.’
    • ‘However, Jon Goodwin, for the board, said work on items such as an extractor fan, fire door, gas flue and expansion joints was incomplete.’
    duct, tube, passage, channel, canal, conduit, shaft, air passage, airway, vent, well
    funnel, chimney, chimney stack, smokestack
    pipe, pipeline, outlet, inlet
    View synonyms
    1. 1.1A channel for conveying heat.
      • ‘These models will have multiple flues for greater heat transfer surface, or a more submerged combustion chamber (so heat doesn't escape to the air, but is transferred to the water instead).’
      • ‘This design has an additional high temperature mass located at the hottest part of the flue to provide several hours of stored heat for the Stirling engine.’
      • ‘As time progressed, these pots evolved into elaborate contraptions made of tin plates with flues and bends to increase heat contact, thus decreasing boiling time.’
      • ‘Older boilers send a lot of the heat they generate out of the flue into the air.’


Late Middle English (denoting the mouthpiece of a hunting horn): of unknown origin. Current senses date from the late 16th century.