Smoke Smell in Basement

[KaiserRolls]

We bought a new (to us) house built in 1970 this summer and were excited to use the fireplace come winter. However, after using the fireplace 5 or 6 times, we've noticed our basement utility room directly beneath the fireplace gets an intense smoke smell about 15-45 minutes after lighting a fire. It's not visibly smoky / hazy - but you can absolutely smell smoke.

I've narrowed down to 2 possible issues but want opinions if i'm missing something.

Possible issue 1: Smoke is back drafting down the ash dump door due to negative pressure in the basement pulling smoke from the firebox to the basement. I did some temporary masonry caulk on the ash door to seal it up about 95% and still had smoke in the basement after lighting a fire to test. This leads me to believe this isn't the culprit.

Possible issue 2: (reference image) Smoke is coming out of the fireplace flue and getting sucked back down the appliance flue due to negative pressure in the basement - especially since the newer furnace is now direct vented out the side of the house. Furnace is not vented out of the flue anymore. Condensation on top of the hot water heater would validate the back draft / negative pressure / air coming back down. I'm thinking the old furnace + hot water heater used to cause enough pressure to get the air moving out and not allow the smoke from the fireplace to come back down.

Attached a visual to help give more context. Even though very rare - i'm leaning towards this being issue # 2.

 

[begreen]

The likely issue is that both flues terminate at the same height so that smoke from the fireplace is being siphoned down the basement flue. The solution is to put an extension on the fireplace flue.

Chimney Flue Extension | Chimney Extension Kit - Rockford Chimney

The Specialty Flue Extension will increase height and draft of your chimney and features an attached chimney cap. Easy to install and ships free.

www.rockfordchimneysupply.com

 

[KaiserRolls]

The likely issue is that both flues terminate at the same height so that smoke from the fireplace is being siphoned down the basement flue. The solution is to put an extension on the fireplace flue.

Chimney Flue Extension | Chimney Extension Kit - Rockford Chimney

The Specialty Flue Extension will increase height and draft of your chimney and features an attached chimney cap. Easy to install and ships free.

www.rockfordchimneysupply.com

Thank you for your input. I'm going to call a local chimney company to see when they can get out. I don't need to be messing around that far up.

 

[begreen]

Thank you for your input. I'm going to call a local chimney company to see when they can get out. I don't need to be messing around that far up.

That's wise. Hope it gets resolved quickly.