Extra Co2 in the garage from WH/Furnace?

So my grow room is built into the garage, prior grows I put a board under the garage door and cut a 6 inch hole in it and braced the temp swings( in the cold of OR) and I am cutting a hole for a dryer vent to exhaust out the side of the house and I realized. I'm going to be drawing air in from my exhaust vent for my water heater and furnace... and its being directed through my room now! Anyone think this will add any beneficial Co2? at a 6 inch rate with LEDs I'll be running it on the low wer flow rate so Hopefully I can get some build up.

without a co2(ppm) meter, it's just a guess obviously..........but gas furnace/water heater will generate a good amount, "free" enrichment might be possible. My levels are double(800+) from outside in winter(closed windows) with all electric appliances in a apt complex just due to people/pets in the building.

now I don't need to tell you that gas burning appliances should be maintained / serviced to ensure safe emissions? also your grow room temps&ppfd need to be high to benefit