General Question

heyrobertdavis's avatar

Why does my fireplace smoke?

Asked by heyrobertdavis (6 points ) September 29th, 2009

chimney is clean, flue is open… still smokes.

Observing members: 0 Composing members: 0

4 Answers

thanatos's avatar

There are several reasons why a fireplace “smokes”.

Usually the size of the firebox (where the fire is) is larger than the flue that serves the fireplace. There is a mathmatical equation that must be followed when a chimney is being built. Most brick masons know this but, sometimes the plans of the house wont allow the proper size of flue to be installed.

According to the National Fire Protection Association, the flue size shall be no less than 1/10th of the size of the fireplace opening. If the flue size is smaller than that, the smoke will back up in the smoke chamber (the area just above the damper) and it will spill into the living space of the house. Kinda like putting ten pounds of crap in a five pound bag! Sorry, i figure that’s the easiest way to explain it.

The cheapest way to correct this problem is with a product called a smoke guard. You can check with your local Chimney Sweep and he can find the right one for you. They come in several sizes from 4 to 8 inches in width. They are a flat piece of steel that is spring loaded and is mounted just under the top of the fireplace opening. They come in black, antique brass, and bright brass. You can also get smoke guards are local fireplace shops. They can be a little tricky to install but, it can be done. After it is installed, you caulk the back side of the smoke guard to keep the smoke from coming around the smoke guard.

Sometimes, you can install a set of glass doors that will also reduce the size of the opening, just make the measurements and check to see if the doors will reduce it enough to stop the problem.

Things to measure: Width of the fireplace opening

Height of the fireplace opening from the floor the top of the opening.

Then, you have to measure the inside of the terra cotta flue that serves the fireplace.

Remember the 1/10th rule and you should be able to solve your problem.

If you feel uneasy about getting on the roof or getting the measurements, just contact your local Chimney Sweep.

breedmitch's avatar

it wants to look cool?

J0E's avatar

Nicotine is addicting.

6rant6's avatar

I’m sure Thantos has great information there, but if you’re new to using this fireplace it could be simpler.

1. Have you made sure that the damper is open? There’s a lever somewhere. You want it closed to keep out cold air when there is no fire, but it has to open when there is one. That’s what the damper does.

2. Have you primed the flue? Light a rolled up piece of newspaper, and hold it as far up the chimney as possible. This starts the air moving up the chimney. Otherwise a “thermal inversion” can keep smoke flowing into your room.

3. Crack open a door or window to allow air to enter the room from outside. If your house is too air tight, air pressure can prevent the escape of smoke through the chimney. It’s pretty easy to diagnose. If closing the window causes smoke to fill the house, you’ll know what to do!

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