I came across this today. It is in the crawlspace, and under a wood buring fireplace. I have not seen this before in WA. Primarily curious if this is common in other states or if you guys can give any more info than my best guess. Best Guess is that it circulates air around and through the fireplace to grab any excess heat possible and introduces it to the heated ducts to aid in air circulation of free heat that would be lost. However, this is simply a guess! Any clarity would be super appreciated. The fan motor is switch controlled from above. There was also a random bare copper wire coming from the crawlspace to the finished interior space, and curious if that may be some sort of thermostatically controlled sensor (like a thermocouple)? This house had all of the high tech things installed that were over the top, in the late 80’s:grinning:
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Seen my far share of fireplace heat chargers sense I was teenager.
Looks safe. Large ducwork though.
Just missing ductwork to draw combustion air from the exterior into the fire place combustion chamber.
Remember, “Ingenuity is the Mother of invention” and still holds true today.
Fireplaces pollute. Chimney requires catalytic converters to bring the fine particle rate down below 2.5 grams per hour in my neck of the woods.
# Montreal’s wood-burning ban starts Oct. 1: What you need to know.)
Robert - to the best of my ability, it simply circulates the air through the fireplace masonry. There were no vents present on the exterior of this chimney…Kind of crazy to me, but really not a bad idea either!
That fellow or mame went to the extreme.
Popular mechanics. A favorite magazine. I use to read fathers.
Seen some large contraptions fashioned out of 45 gallon drums the heat exchange, mechanical bellows below, as in your image, a 120V -1/3HP motor and 5 inch galvanized steel duct work attached to a solid fuel furnace during 1 rural inspection.
Marcel Cyr, being in Maine, must has seen plenty.
Thanks for sharing.
Any crack or hole and carbon monoxide, etc., is circulating through the house from what I can see. It may be a safety concern but I can’t really see much of it.
It is just something to think about.
Larry Kage - Phenomenal point I have now listed as a potential hazard, & thank you for the input.
And when you open the door to add wood or if the door leaks, smoke spilling would get circulated into the home. I would recommend to have it inspected by a professional.
Based on what observation/fact/ or measurement?
This is a heat recovery system.
Do you know that HVAC air ducts cause 90% of all indoor air issues associated with indoor air quality?
Do you know that air ducts leak 30% on a good day?
We use “Aeroseal” to correct these issues.
Who do you recommend should inspect further, the guys that do it wrong in the first place?
Did you light a fire (against all HI SOP and insurance policy) and test for CO?
Did you do an air pressure test on the system for leakage (which is not part of the HI SOP)?
If you did not, why are you talking about this? If you did not do the required testing to make a recommendation (because it is outside of your job), why are you talking about things outside of your job?
David, no fire lit, and not tested. It was there in the crawl and simply trying to explain to the client what it had a function for. At this point, the wood burner is de-commisioned, and there is a gas insert in it’s place.
How dare you! who do you think you are!? gas insert specialist? did you inspect it to NFPA standards!? How about CSIA level 2 specs? did you pressurize the duct to see if it can handle excessive build up of smoke? You’re not AHJ, you have no idea what was approved and what wasn’t! Leave everything to the pros, stick to home inspection! Wait… never mind. 
PS: dare not mention code, I’m gonna self-combust