Why do fireplaces smoke, and how can you cure the problem of a smoking fireplace.
Fireplaces generally smoke for four reasons:
1 Ventilation to the room
There may be no ventilation, or inadequate ventilation to the room. If the fireplace stops smoking when you open a window in the room then this is the most likely cause. For most ventilation applications use a Black Hole Ventilator. This is easy to install.
2 Fireplace or chimney size
Your fireplace opening is too big for your chimney or liner. If the fire stops smoking when you cover a portion of the opening up, then this may be the cause. Make sure you eliminate other causes of smoking first, as covering part of the opening would tend to lessen smoking even if the size of the fireplace opening is not the problem. You can reduce the size of your fireplace opening by using a fireplace fret, or by installing a canopy across the top of your fireplace opening.
Refer to our Fireplace & Chimney opening sizes page.
Downdraught is when the wind blows down your chimney. This usually happens in puffs rather than being continuous. To prevent downdraught you can try several things: fit an antidowndraught cowl to your chimney pot, or fit a taller chimney pot if possible. (Downdraught can be caused by wind eddies close to buildings or structures - raising the chimney pot can raise the end of the chimney away from these eddies.)
4 Vacuum effect
There are two types:
a - often unused fireplaces in rooms with inadequate or no ventilation can suck air from the fireplace you are using. To stop this, cap all unused fireplaces at the chimney pot with a flue ventilator (a cast clay insert that simply sits in your chimney pot). Then make sure that if there are metal baffles in any of the other fireplaces that you close them if the fireplace is not in use. Similarly close the door of a stove if it is not in use. (In summer, when no fires are lit, you should leave baffles and stove doors slightly open to allow ventilation to your chimneys).
b - very rarely, air can be sucked from one part of the your building due to prevailing winds. The air will choose the path of least resistance which will probably be down your chimney and so your fire will smoke. There is not much you can do about this, other than installing an Exhausto fan - a unique fan designed to suck high temperature smoke out of your chimney. You install this on top of your chimney.