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    • Air Starvation
    • Down Draft
    • Flue Sizing
    • Raising a Fire Basket
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Argyles Chimney Solutions

Restrictions that cause a fireplace to smoke

What do we mean by a Restriction ?

Anything that reduces the capacity of the flue causing a poor draw or flow rate causing the gasses to fill the chimney and spill out into the room. There are many causes and most are very obvious;
  • Fitting a pot or cowl that is smaller than the diameter of the flue
  • Fitting  a capping/ half pipe to the top of the pot.
  • Fitting the wrong terminal
  • Blockage by birds nest or debris
  •  Casting a flat concrete ceiling or register plate during alteration
  • The original Flue been lined and is now too small for the opening
Picture
 The flat surfaces around this new  flue  prevented it functioning  correctly.
Restrictions.
​
A simple task of looking up the chimney with a torch can reveal obvious visible blockages like dampers, chimney valves, balloons or bags of straw but we also check the pot or terminal serving the fireplace and make sure there are no close fitting vents which will allow a draw but prevent normal function.  The terminal below for example will not allow proper function but acts as a vent.
Other cowls may have been fitted in an attempt to make the flue system work such as Anti-downdraft, or Spinning Cowls can cause a restriction on large flues but I would not normally recommend their removal for testing unless it is easy to do so. 
If the flue has been lined and there is a flat concrete pad supporting the flue invariably this will be the cause of smoke spillage but in most cases the Tin Foil test will overcome the restriction .
Pots may have been added that are too small or when fitted steel bars or slates placed across the flue to support the pot, these could be partially blocking the flue causing smoke spillage into the room . 

A Camera Survey will help you to pick up all of these restrictions and equate them into your findings. 

Examples
  • In the winter last year we had this negative sheet test response on a large fireplace with a tall chimney of original construction, the draw did not exist but the camera inspection revealed that the builder had used a piece of slate to support the chimney pot whilst the cement holding it set.  Unfortunately the slate was not removed afterward and more than 50% of the flue was totally blocked.
  • On one occasion after completing the initial tests in a relatively new house a camera survey revealed a bag containing a MacDonalds Burger and Chips wedged on one of the bends blocking the flue.  Perfectly intact, no burn marks just well dried out!
  • In another recently the flue had been altered at ceiling level and moved to the right horizontally, soot falling on the flat area built up reducing the capacity of the flue and it smoked out after every six weeks of use .. almost to the day!​


Some examples of restrictions to a flue
Picture
 This is the correct gap between the top of the 300mm flue and the Dovecote capping
Picture
The 100mm gap above the flue prevented the system functioning .
Picture
1.   Looking down a blocked chimney pot
Picture
2. The central pot had to be re-positioned 
Picture
3. The internal edges reducing the flue size       on the other pots are being removed
Picture
This is a venting cap or insert.  It is only placed on top of the pot when the flue and fire are not in use.  
Picture
This view  looking up the chimney from the fireplace shows bricks that have fallen from above and blocked the flue
  • Home
    • Terms and Conditions
  • Smoking Fireplaces
    • Diagnose Smoking Fireplace
    • The Draw Test
    • The Tinfoil Test
    • Restrictions
    • Chimney pots
    • Ventilation Problems
    • Air Starvation
    • Down Draft
    • Flue Sizing
    • Raising a Fire Basket
  • Chimney Camera Surveys
    • Birds Nests
    • Camera survey equipment
  • Glass Canopies & Panels
  • On the job
  • Contact