My fireplace smokes while in use

Posted by Dave on Oct 30th, 2009 | no comments

If  your fireplace  smokes into the room, here are questions to ask youself  that may  assist in determining the source of the problem .

Note: We provide and install virtually every product and service to correst chimney defects and enhance the efficiency,  beauty and joy of your fireplace, insert or stove. 

   IF YOU NOTICE SMOKE COMING OUT ANOTHER FIREPLACE WHICH IS NOT BEING USED, OR SMOKE OR SMOKEY ODORS IN ANY OTHER ROOM OR LEAKING FROM AROUND THE MANTEL OR ANY OTHER UNUSUAL PLACE, PUT OUT THE FRIE IMMEDIATELY.  Call us for an evaluation and have the chimney repaired before using it again.

  IF YOU SUSPECT A FIRE OR EVEN SMOLDERING IS OCCURRING ANYWHERE OTHER THAN INSIDE THE FIREPLACE CALL THE FIRE DEPARTMENT AND PREPARE YOUR FAMILY TO EVACUATE THE HOUSE IMMEDIATELY! Call us for repairing your chimney before using it again.

Does your fireplace smoke during the first few to several minutes? (Includes smokes so much when I try lighting a fire that I have never been able to get a fire going for any length of time.)

 If yes:  There could be multiple problems, but the first thing I do is determine if it is a down draft  or “cold hearth syndrome.” This means the cold air in the chimney and outside would rather drop down than go up, when you open the damper. (Hence if the damper leaks, even the slightest, the hearth area is always cold.)

  Open the damper. If you will immediately feel cold air dropping down the chimney, try warming the flue by rolling up come newspaper in a cone and lighting the larger end, making a torch.  Having your DAMPER OPEN, hold the newspaper up high, warming the flue. The smoke may back up for a few seconds, then it should rise. 

  I like to have some loosely crumpled newspaper in the fireplace to light quickly thereafter to maintain a constant source of heat. In severe cases a lot of constant heat is necessary.

  If you feel a strong  rush of cold air when you open your damper, this procedure will be difficult and may not seem to work. Under severe circumstances, I burn a lot of newspaper, start it really fast and sometimes even need to place several sheets up into the throat (bottom damper) area.

  If you try this, be careful. when the paper burns it will shrink and fall down. A competitor tried this in an old sooty chimney that had not been in use for years and started a chimney fire.

  If you are unsuccessful,  or prefer not to take any risks, call us and we can have a look. If this helps, but smoke continues to enter the room indefinitely, you also have another problem.

Does your fireplace continue to smoke  after several minutes of use? Or do you only notice smoke after several minutes or a few hours?    Or do you only notice a smokey smell? If any of these are true, you may have a flue liner to fireplace opening size ratio issue. You may also have a wind or a fire placement issue.

  Fire  placement issues are simple. Place your log grate all the way to the rear of the fireplaceand in the center, left to right. Some people report  that placing a brick under the legs of the grate helps. If that works, your done.

  If you don’t like it so far back, you either live with it or read on and hope resizing or a fan helps. I suggest being delighted it works now.

 If the smoke is intermittent, see if it only occurs on windy days or on days that the wind blows from a particular direction. If so, your chimney may be too short or there may be tall trees nearby.  Houses on hills, in valleys or in areas where trees are clear cut,  like bare, new developments or farms, seem to have increased likely hood of wind related smoke problems.

  Raising the chimney is important if it is shorter than code. (3 feet above the roof,minimum and at least 2 feet taller than any part of the house or neighboring buildings within a 10 foot radius of the center of the flue opening.

  If you meet this standard, I suggest not building the chimney higher and higher until the smoke stops. It might not stop and this is an expensive approach. Raising the chimney to code may not help either, but at least you have met a legal safety code requirement.

  Wind related problems can be resolved with fans (remember they are expensive and audible) or with directional chimney covers.

  Turbines or rotary roof ventilators are not a good solution. They have to spin really fast too help and often the wind is not strong enough to spin it that fast. They also often develop squeaky or frozen bearings quickly in this application.

  “Vacustack “  brand chimney caps are supposed to correct draft problems caused bt wind. I have had  some success with them. My guess is that sometimes the wind problems are coupled with non wind related issues such as cold hearth syndrome which is a pressure differential issue and a vacuustack is not designed correct this problem.

  I like “Hazel” vents. They are helmet shaped caps with a weather vane on the bck always directing the opening away from the wind. They do not increase draft, they simply turn away from the wind. Having no bearings, the cap pivots on a single pinpoint rod which is protected from the elements by the cap itself. I’ve never seen one get stuck.

  Sometimes the reason a chimney is very wind sensitive is that there are also sizing issues as discussed below and once these are addressed, the wind issues  diminish.

    The most common  problem causing  smokey fireplaces, well after the fire is lit, is that the flue liner is too small, there is a restriction of some sort in the chimney, or the damper is not open fully. It is rare that the chimney is in need of cleaning, except in the case of wood or coal stoves. They clog  mesh at the top of the chimney and the chimney as well.

  Clogged Mesh usually indicates chimney cleaning is overdue!

  There is an optimal fireplace opening size to chimney liner size ratio which is 10 to 1. This means the fireplace opening, measured in square inches, is 10 times greater than the flue liner opening. With fireplaces having chimneys over 20 or 30 feet tall, with fireplace chimneys chimneys having  round or very straight liners,  these fireplaces chimneys may draft well with 12 to 1 or even 14 to 1 ratios. 

  Another way of  looking at a ratio problem is that the fireplace is too big. A smoke gaurd, or metal plate, or some other noncombustible and heat resistant material can be used to block off a few inches or more across the top of the top of the fireplace opening to make the fireplace smaller and correct ratio related smoke problems.

   Electric fans made for chimneys are available to correct smoke problems. They are well made and fix almost every smoke problem, if sized properly. But, though they are advertized as silent, they are always very audlible. We use them in cases and when a smoke gaurd is either aesthetically not feasable or when a smoke gaurd  is not enough to correct the problem.

  In some cases we actually make the fireplace smaller. This is very common in historic renovations such as with coal burning fireplace to wood burning fireplace conversions, but is always a possible alternative to other methods of correcting smoke problems resulting from incorrect flue liner to fireplace opening ratios.

  Fireplaces with very short chimneys and short chimneys with very large liners, sometimes smoke into the room even though the liner to opening ratio is correct. I don’t like to make these chimneys taller unless I test the chimney first by adding a length of pipe to the chimney “proves” extending the chimney will correct the problem. 

   Raising chimneys is a lot of work and many people report that doing so did not totally correct their smoke problem. In these cases, smoke gaurds are inexpensive and exhuast fans always work.

  Does your freplace smoke  when the fire is going out after a brief fire? or after a fire of 2 hours or longer?

  If it only smokes after a brief fire is dying down, don’t have brief fires or read on to the next paragraph for possible solutions.

  If the fireplace smokes after burning fires in excess of 2 hours,your chimney has warmed up and the residual heat emmitted from the warm chimney is not enough to sustain a draft until the embers are no longer smoking. You have a pressure related problem and it will be hard to stop without a chimney exhaust fan.

  Other possible solutions include cracking windows on the lower levels of the house, sealing crevices around exterior doors and windows on upper levels of your house, supplying make up air for your heating appliances and installing not perfectly air tight, but marketed as air tight, glass doors. Read my article on chimney odors. This is a simlar problem with similar causes and solutions as “smoke odors after the fire is out.”

  Does your fireplace stop smoking into the room when you crack a window?

  This is a pressure related issue and can be resolved by providing makeup air to the house.  That’s what cracking the window does. If you measure how many square inches your widow needs to be open, a make up air supply of the same size should fiz the problem. Usually they are installed in an exterior wall and provide air into the furnace area.

  An outside air supplly for the fireplace may help a little, but they are generally  small and may not provide enough air to adequately eliminate the smoke.  Again chimney exhaust fans always work, but are pricey and audible and must be used on a relatively high speed setting as they restrict air flow otherwise.

Call 301chimney for a professional analysis now

Dave Myers

CEO  of 301Chimney