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Question DetailsAsked on 11/15/2013

How can we eliminate odor and improve heat from a basement fireplace? Can we remove soot baked onto the box?

We removed a fireplace insert a few years ago because it did not meet current code, installed new dampers at both the top and bottom of the chimney flue, and added a fresh air intake and glass doors. We get absolutely no heat when burning a fire now and still have odors coming into the basement when it's damp and windy outside. The firebox is glazed with black soot from the insert that is unsightly and may contribute to the odor problem.

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If the deposit is thick, scrape off first with putty knife or wide, stiff wire brush after wetting with a degreasing cleanser like 401. Some people use oven cleaner, but that makes for quite a poisonous odor while working and till a couple of fires have burned, so I would not recommend that. For real difficult spots non-flammable brake cleaner (from an auto parts store) really takes soot and creosote off fast, but breathing the fumes is a problem unless you have a chemical fume respirator - and even then avoid as much exposure as possible, as it can harm eyes. Do NOT use a flammable part cleaner, as if it leaks through the brick or metal lining, you could get a fire spreading outside the firebox when you first light the fire.

Then, using old towels around the edge of the bottom to trap the liquid (so it does not leak all over outside the firebox) use a spray-on firebox soot and creosote cleaner and stiff scrub brush (old- shoe or horse brush type) to clean it off. For the back half, first burning a good fire of small dry sticks started with a dozen or so double-width sheets of wadded up newspaper will typically burn it off nicely too, just don't get too carried away with the size of the fire and just for a very short time, as newspaper burns a lot hotter than normal logs, and of course keep it far enough back it does not lap out the front and start your mantle on fire.

I presume you are locking the damper, not just letting it drop closed. Some people do not realize a proper damper will close when you pull (or push, for some) the damper handle or ring, but you then have to go further quite hard to operate the cam mechanism that forces the damper down tight. If it is latching tight, when you open it there should be a pop or thunk sound as you release the cam, then it swings up - if it swings easily right from the start, then the cam mechanism is not latching it down tight, so you will have a lot of air leaks.

The odor from downdrafting during cold, windy days indicates your damper is not sealing right - you need a chimney sweep for that. Depending on your fireplace design, there are molded edge strips that can be used on some to make them seal, on others it requires use of a product I forget the name of, but is like a liquid steel product where he aggressively cleans the sealing surface, sprays a bond-breaking oil on the damper, puts on a thick bead of the sealer product, then closes the damper on it latched tight so it squeezes down and exactly fits the gap under the damper.

One thing you can do to reduce the downdrafting also, and reduce the amount of rain water getting into your chimney on rainy/snowy days, is have the finest screen allowed placed around your chimney top, making sure of course that the rain now hitting it and being stopped there drains off to the outside and not down into the chimney. Generally chimney soot does not smell much - just slightly like wood ashes - but wet soot can really stink.

One question I do have, if you have both bottom and top dampers, how do you operate the top one ? If through a cable down the flue into the firebox, then that is keeping your lower damper from closing totally, sort of defeating the purpose. That also lets cold air in the flue drop down, bringing with it odors.

As to the lack of heat - if you have an outside air source and glass doors, you should be getting almost no heat, because you have built a sealed firebox system. When you want heat (rather than just maybe a nice glowing bed of coals), the glass doors have to be open - otherwise you are stopping much of the heat you are wanting. Also, if you close the air damper (usually a slide knob at the bottom of the glass front unit) once the fire is truly out, odors from the creosote will not get into the house so easy.

Answered 6 years ago by LCD

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