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Michigan State University Extension
Home Maintenance And Repair - 01500597
06/24/03

Smoke Problems



If a stove or fireplace is letting smoke into the house first make sure that the flue gas dampers are open. If the dampers are open, then the best way to solve the immediate problem is to open a window or door on the first floor or basement while at the same time close all openings in the upper parts of the house. If the weather is windy, the open windows or doors should be on the windward side of the house. To keep smoke from entering a room, turn off kitchen and bathroom exhaust fans and close forced air heating registers that are near the fireplace.

If the chimney serves a stove, move the stove closer to the chimney and eliminate elbows in the stovepipe connector. If the chimney serves a fireplace, the only solution may be to make the fireplace opening smaller. This can be done by raising the hearth or installing a canopy hood down from the top of the fireplace opening.Prefabricated chimneys can be made taller by adding another section or two. Weather stripping or otherwise sealing upstairs windows and attic doors can help.

If you tried these remedies and smoking still occurs, the only remedies are either a smaller stove or fireplace, or a new chimney. Increasing the diameter of the chimney is the surest way to get more capacity.

Problem

Smoke coming out of stove while first starting up in cold weather.

Cause
Temperature differential between outdoors and indoors causing changes in air movement in the house to equalize that of the outside pressure. The air in the house becomes buoyant, drawing air from the chimney (reverse chimney flow); or not enough air to supply fire. Remedy

Open a window near the stove (easiest, safest). Provide a separate air inlet. or Place a lighted newspaper in the stove pipe inlet.

Problem
Smoke coming out of stove or fireplace when windy.

Cause
Wind currents force air back down the chimney. Nearby trees, buildings in roof projections often cause downdrafts during windy periods.

Remedy
Check chimney for correct height in relation to nearby objects. Remove nearby obstructions. Place a chimney cap on chimney. If there is an existing cap, try a cap of different design. Change chimney height.

Problem
Smoke continuously out of stove or fireplace.

Cause
Blocked flow of flue gases or flues partially filled with soot and creosote; or the flue may not be large enough to carry the smoke and gases outside; or green or wet wood can cause smoke since heat is used to dry the wood, also softwoods can cause smoke because of the resin in wood; or the flue may be too large (in older houses which have a large central chimney with several fireplaces and flue openings, there may not be enough draft to keep the column of smoke rising if only one fireplace or stove is used); or not enough air for efficient combustion; or cracks or leaks in flue lining.

Remedy
Check chimney for obstacles (bird-nests, branches, leaves, etc.). Clean the chimney. Install a large flue or attach a smaller appliance. Keep hot fire going; use seasoned dry wood or split the green wood finer and mix it with dry wood. Reduce the cross sectional area at the top of the chimney or install a stove pipe through the center of the chimney. Provide a separate air inlet for wood burning appliances. Check flue liners. Install a smoke shelf in fireplace.

Problem
Smoke coming out of one fireplace while another wood stove or fireplace is in use.

Cause
Two wood burning appliances sharing the same flue may result in smoke traveling from one appliance to another. If each appliance has a separate flue, there may be smoke leaking from an adjacent liner to the liner serving the other appliance. If the flue height in adjacent liners is equal at the chimney cap, smoke can be pushed or sucked down another liner.

Remedy
Either disconnect one appliance or plug the fireplace opening if two appliances are sharing same fireplace flue. Add a separate flue for each appliance. Check for breaks in adjoining flues or stagger flue joints. Change height of nearby flues extending out the chimney.

References

This information comes from Michigan State University Extension bulletin E-1389, Smoke Problems and Their Cures.

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