Musty smell from unvented firebox

[JustADude]

Home is about 3-4 yrs old. Unvented firebox is on outer wall, but well sheltered. Musty smell appears to be coming from lower vents. It is a noncirculating model and has not been run for the year.

I removed a the front refractory panel and control access cover and looked into the lower vent area. I did not notice anything unusual, but could definitely smell a musty type smell.

We are on a slab house and this is in the elevated portion of the slab.

Are there any suggestions about how to reduce or eliminate the musty smell?

Thanks for any feedback and insights.

[JustADude]

Well after looking a little closer at the area where the unvented firebox is installed I noticed that it is essentially an 5'x5'x8' confined area. It is closed off at the top, but I can access it from the attic.

Would it being an enclosed area have anything to do with the musty smell or is there another concern with the foundation or something else?

Thanks again for any thoughts.

[HayZee518]

an unvented firebox -i.e. propane - produces co-2 and water vapor. there MUST be a suitable supply of oxygen otherwise carbon monoxide will be produced and this will kill you. large amounts of c0-2 also will as co-2 doesn't support life. dampness is produced from water vapor in the air and a faint smell of propane is generated with all non vented appliances. there must be a source of make up air coming into a room fired by a non vented appliance.

[JustADude]

HayZee518,


Thank you very much for your post and that may have something to do with the odor, but the odor was present prior to running the fire. Prior to the 1st post shown below, we had not run the fire this year, i.e. 10 months without running the fire, and the musty smell was very strong and present coming from the lower vent. It smells like a dank smell is seeping up through the slab and then through the lower vent.

Thanks again.

[HayZee518]

if could verywell be that - if there is no insulation board under the slab, ground water is continually being drawn up into the concrete even though it's fully cured.

[pushkins]

Run the fireplace for a couple of hours, then check to see if the smell is still there the next morning. If it is damp (ish) concrete then the fire running should dry it out fairly quickly.
I see what Hayzee is talking about fairly often, builder didn't put any moisture barrier down under concrete slabs, moisture is absorbed into the concrete, but not enough to make it "wet". Fire boxes are usually dank little holes in the wall so not a lot of air circulation happens then the smell comes.
In the off season to using the fire get your self one of those moisture absorbing containers, the ones that have the gel or crystals that absorb moisture from closets etc... ( I cannot remember their name right now), put it at the back of the fire box, problem solved for the off season.

[HayZee518]

there are two chemicals that absorb moisture. One is called calcium chloride the other is sodium polyacrylate.