Why does smoke come out of a chimney?

Why does smoke come out of a chimney?

On some occasions, we may be unpleasantly surprised to find that when we light our fireplace, the combustion smoke does not go up the chimney but instead leaks into the interior, at least partially. The reasons why wood-burning fireplaces can have this problem vary, depending on whether it is a newly installed chimney or one that worked perfectly the previous season.

Reasons why a chimney can let smoke into the interior

The chimney flue

Sometimes, the chimney flue is obstructed by something. For example, there are cases where birds have built a nest, a bag has gotten into the duct, or a grate has become blocked due to accumulated soot. To address this issue, simply make sure that the chimney flue is free of any elements that might block the passage.

Difference in temperatures

In other cases, the entry of smoke is due to a difference in temperatures. When the chimney is cold and it is lit, the smoke tries to move the air above it, but since it is at a lower temperature, it seeks the easiest way out and seeps into the room. As the chimney and flue heat up, the smoke exits from the top. To prevent this from happening, it is recommended to use thin firewood, which will quickly heat up the chimney, and then add thicker logs.

The flue in a stove or fireplace

Waiting for the door to close

Certain fireplace models such as inserts or cassettes produce smoke because as soon as the fire is lit, the door closes. This fills the interior with smoke, and since the set is still cold, it exits through any opening or gap. To prevent this, the best thing to do is to leave the door slightly ajar until it reaches temperature and then close it a couple of minutes later.

Poor placement

Some people install the chimney outlet near the kitchen’s smoke extractor. If the chimney doesn’t have a door, the smoke will be attracted to the extractor, leading it to enter the room. If that’s the case, it should be avoided to light it while the chimney is in use.

Other reasons why smoke enters the interior

There are other causes for smoke to enter. For example, a narrow outlet that cannot handle the amount of smoke generated by the chimney, damp firewood that produces more smoke than usual, or low-quality firewood.

How to prevent smoke from escaping outside

There is a way to reduce the chances of smoke entering the room. Our fireplace doors seal the front part in such a way that there are no cracks for the smoke to escape through, forcing it to always exit through the chimney. This, combined with the glass for fireplaces they are made of, allows you to maintain control of the flames and check that the fire is in optimal conditions, reducing the amount of firewood consumed and the smoke generated.

How does a chimney smoke extractor work?