Wouldn't feeding the CO into the burner upset the air/fuel ratio? OTOH, might it act as kind of an EGR analog, dropping the NOx emissions of the furnace? Hmmm...
It will create a dangerous condition.
#1. It will screw up the a/f ratio of the furnace.
#2. It is virtually impossible to remove all lint from the air. You could cause a fire in your furnace, and burn the house down. At the very least ash from the burnt lint will clog up the flue and burner box of the furnace.
CO should only be present if the air fuel ratio is messed up. I grew up with gas space heaters that didn't vent to the outside. We had CO alarms but who knows if they worked. By the time you relize they don't you usually already have problems lol
Working on other peoples furnaces out here on the East Coast, I found many mini gas funaces that have no vent at all, you can still buy them and they are ment for single room heating. I was always puzzled how could they just vent natural gas exhaust right into the room. The vent has a 90% valve, it has a small amont of exhaust that still exits the basement, but 90% still goes in there. So far after heating the house last year, the Co2 detector never went off and I didn't turn blue. lol