Chimney Corners

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Smoking Fireplace Chimney

Smoking Problems While Burning

 

Smoking problems while burning are often the easiest to diagnose and sometimes the most difficult to correct. Many smoking problems are the result of improper construction or design. Below is a description of the common design problems which may lead to smoking problems.

 

Damper is Not Fully Open

 

Check to see if the damper is open all the way and functioning properly. More people overlook this step than you would think!

 

Inadequate Air Supply

 

Open a window or door as close to the fireplace as possible. If the smoking lessens or stops when the door or window is open, the problem may be inadequate air supply. Homes today are designed to be as air-tight and energy efficient as possible. The flow of air up the chimney cannot exceed the flow of air into the house. As air leaves the room during the burning process it must be replaced by fresh outside air. This air would normally enter the house through small cracks in the doors and windows.

Many fireplaces being installed in homes recently come with an “outside air source”. A lever or handle will usually be found in or near the fireplace. This can be opened to allow fresh air into the firebox to replace the “room air” that is being used. If your fireplace does not have an outside air source, it may be possible to install one in masonry fireplaces. We do not do this work.

 

Fireplace Opening is Too Large

 

This problem typically allows the fire to burn comfortably for a while, but the room will become smoky after some time.  The fireplace opening should be sized based upon a relationship with the chimney flue tiles. An ideal fireplace opening would be no more than ten times the cross sectional area of the chimney flue. For example, if the inside dimensions of the flue tiles are 10 x 10 equaling 100 square inches, then the fireplace opening should not exceed 10 times this or 1000 square inches. 


If a fireplace opening is too large, it will allow more air into the firebox than the flue can exhaust. If the opening is only slightly larger than it should be there is an easy fix for the problem. Installing a Smoke Guard at the top of the fireplace opening will reduce the effective opening of the fireplace. 


You can try a temporary Smoke Guard yourself before purchasing a permanent Smoke Guard. To do this, cut a strip of tin foil several inches longer than the width of the fireplace, and tape it to the top of the fireplace opening. As depicted in the picture above, cover the top of the fireplace, shortening the height by approximately four inches. Try burning a fire on a cold night; if decreasing the size of the fireplace helps to improve your draft, a permanent Smoke Guard could be the solution for you. 
The Chimney Flue is Obstructed
 

Extinguish the fire and look for obstructions. Animal nests are commonly found in chimneys and can often be large enough to restrict flow. Please visit our "Chimney Caps" section to learn more about how to prevent animals from entering your chimney. 


Soot and creosote can build up and plug or restrict the airflow of your chimney. Also, in antique chimneys, fallen brick or mortar may be obstructing the flue. A blocked chimney is a fire hazard and should never be used until the obstruction is removed and the chimney flue is cleaned and inspected.


 

Improper Construction or Design

 

It is possible that a masonry chimney was poorly designed. If your fireplace consistently smokes and none of the ideas presented above work, it may be that your chimney has design flaws. Please contact our office about this.

 

Occasional Smoking Problems

 

Occasional smoking problems are often the most difficult to diagnose, but most are simple to correct. If you are having occasional problems with the fireplace draft, there are several factors that could be causing the trouble. Paying close attention to the circumstances surrounding the draft issues can help to diagnose the problem and find the best solution for you. 

Temperature

 

If the temperature outside is fairly close to the inside temperature and there is a high pressure cell in the area, you probably do not have enough air pressure in the house to maintain a draft. 

 

Competing Vents from other Appliances

 

Check for the existence of competing vents. Kitchen and bathroom fans, and chimneys for other fireplaces or stoves may overpower your chimney’s draft by drawing the air they need through the “smoking” chimney. This problem can be solved by ensuring that each vent has adequate air flow. If the house is two or more stories, hot air rising and escaping from the top story can reduce the air pressure of the ground floor, and may pull replacement air through the chimney.

 
 

Wood Supply 

 
Check your wood. Excess sap or moisture in the wood can be one problem. Dense woods which are hard to light can cause an initially cool fire which can result in poor draft and excessive smoke.

 

Chimney Height


Measure the height of your chimney above the top of the fireplace opening. Any chimney with an effective height of less then 10 feet will generally cause problems. The chimney or vent pipe must extend above the roof at least 3 feet.  Also, the top of the chimney must be 2 feet higher than any roof line within a 10 foot radius.
 
 

Chimney Caps

 

The lid of your chimney cap should be at least six inches above the tallest flue tile. Cap lids that are close to the top of the tiles can cause restriction of the escaping smoke and gases.