Here are some of the most common causes of smoke problems. Simply find the symptom that most fits your situation. If you don’t know the exact conditions which are leading to your problem, just follow through each diagnosis until you solve the problem. It is possible, and even probable, that your fireplace is suffering from more than one problem. Many times, where a single problem is not sufficient to cause back-puffing, several combined will. If this is the case, each problem will have to be tracked down and cured separately. Should none of these work, do not let the pack-puffing continue!
Contact a chimney professional for further assistance in diagnosing the problem and prescribing the cure.
Problem: Constant Smoking
Is your damper open? If it is and the smoking continues, open a nearby window as close to the fireplace as possible. If the smoking lessens or stops when the window is opened the problem may be inadequate air supply.
Homes today are designed or modified to be as airtight as possible. The flow of air up the chimney can not exceed the flow of air into the house. All air removed from the room must be replaced by fresh outside air. This air normally enters the home through small cracks and imperfections in doors, windows, and walls.
Experiment until you have found the smallest effective window opening that eliminates the problem. You can either leave the window open to that degree while the fire is burning, or install a fresh air duct. A fresh air duct will eliminate the mixing of could outside air with the warm room air. If you install a duct, be certain it has the same cross-sectional area opening as the open window setting found to be effective. Also be sure to add valve or close off to allow for sealing of the duct when not in use.
Extinguish the fire and look for interior obstructions. A chimney may be clogged by a squirrel or bird nest. Soot and creosote can plug or restrict the air flow. If the chimney is older, the problem may be structural failure. Fallen bricks, mortar, or metal may be obstructing the flue.
All obstructions must be removed. A blocked chimney is a fire hazard and should never be used until completely cleaned and inspected. Chimneys blocked as a result of structural failure should be condemned and rebuilt or relined with a chimney relining system.
If you have a wood stove and your chimney cap has a screen, there is a chance the screen is clogged with creosote. Clean it with a scrapper and steel wire brush. Also, check your wood burning habits and the condition of the wood. If this doesn’t seem to be the problem, consult a chimney professional. There could be a problem with your installation.
Problem: Erratic Smoking:
What is the weather like outside? If the outside temperature is fairly close to the inside temperature and there is a high pressure cell in your area, you probably don’t have enough air pressure in the house to maintain a draft. The solution here is to wait for the weather to change.
Check for the existence of competing vents. Kitchen and bathroom fans, or chimneys for other stoves or fireplaces may overpower the chimney by drawing the air they need in through the chimney when you’re wanting the smoke to go out. To solve this, make sure each vent has adequate airflow.
If the house is two or more stories, hot air rising and escaping from the top story (due to an open window, poor insulation, major leaks, etc.) can reduce the air pressure of the ground floor and pull air in from the outside, even back down the chimney.
Problem: Erratic Smoking With Hard To Light Fires
Check your wood. Excess moisture in the wood can be one problem. Dense wood, which is hard to light, can cause an initially cool fire which can result in poor draft and excessive smoke.
On wood stoves, check your damper opening or draft setting. An opening that is either too large or too small can result in incomplete combustion. Experiment until you find the smallest effective settings.
While experimenting, don’t make drastic changes. The key is consistency and moderation in making your adjustments. Make small adjustments spaced well apart. This gives the fire time to adapt to the new setting before you make any further adjustments.
Check to see if the draft is actually passing through the fire. Move a smoldering stick of lit match around the firebox opening of the fireplace, or around the outside of the wood stove. Deflections in the smoke will indicate air being sucked toward the fire.
In fireplaces, the draft should funnel inward and upward and be strongest near the floor. Fresh air should surround and be drawn into the fire, forming a narrow, fast moving column of air near the damper. If you find that the draft is missing the fire, wait until everything has cooled off and then adjust the height of the grate.
Analyze your start up procedure. Pay special attention to loading patterns and kindling use.
Problem: Smoking Occurs In Light Breezes:
Measure your flue’s dimensions when the fire is out. For wood stoves, be certain the flue size matches the vent lip to which the stovepipe attaches, or matches the flue size recommended by the manufacturer.
In a fireplace, the rule of thumb is that the opening of the fireplace should be no larger than ten times the flue area. The area of a rectangular flue can be determined by multiplying the lengths of any two adjacent sides. For instance, a flue tile with an inside dimension of 6” x 11” has an area of 66 square inches. To find the area of a round flue, begin by measuring the diameter and dividing it by two. This gives you the radius. Multiply the radius by itself, and then take that answer and multiply it by 3.14. This gives you the area of a circle.
To determine the firebox opening, multiply its height by its width. Now divide this by 10. This should give the minimum flue opening.
For wood stoves, there are a couple of options for a too small opening. One is to rebuild the chimney, by replacing the too small flue with the proper size flue liner. The other is to have a prefab system installed for the woodstove. For fireplaces, the remedy is to reduce the fireplace opening. This can be done by asking your chimney professional to install glass doors, install a product to lower the fireplace opening, or lower the lintel.
Measure the effective height of your chimney. This include only the part of the chimney that starts above the point where the wood burner enters the chimney.
Requirements for proper height vary considerably. Factors which affect proper height are climate, surrounding landscape, prevailing winds, altitude, etc. Any chimney with an effective height of less than ten feet will generally cause problems. Also make certain the top of the chimney is at least two feet higher than the highest point within ten feet of the chimney.
Problem: Smoking Occurs In Heavy Winds
Check for obstructions that might form a downdraft. Roof lines, trees, hills, or nearby structures can all cause downdraft problems. When the wind blows over and down around them, the downdraft simply blows down the flue, sending the smoke into the house. A chimney cap will reduce the effect of these near vertical blasts of wind.
Problem: Smoking Occurs When Glass Doors Or Stove Doors Are Opened:
This is most often cured by simply opening the doors very slowly, allowing the airflow to adjust in the firebox. Opening the draft control several minutes prior to opening the doors will raise the temperature and eliminate a lot of the smoke, reducing chances of back puffing when the door is opened.
Problem: Smoking Occurs When Household Doors Are Opened
A household door opened or closed too rapidly can result in a change in your home’s air pressure, causing the draft to briefly stop or even reverse. This is more often a problem with fireplaces than wood stoves. A temporary solution would be to use hydraulic door closers. A permanent solution is to provide your fire with its own independent air supply.
Another problem can result from inward opening doors fanning the air, resulting in momentary back puffing. A high backed chair of screen placed between the door and wood burner may cure the problem.