If it runs on anything that comes out the ground (oil, natural gas, propane, etc) it creates CO. If the pipe coming out goes to a chimney or stack, it's the exhaust.
I'm no expert, but have researched the issue with a recent remodel. For example, in my city, I could not add a kitchen fan over 300cfm with out adding make up air for combustion. CFM is measured as output, which may be less that the rated cfm of the fan. Need for make up air is also a function of how many other appliances in the home exhaust (bathroom fans, clothes dryer, and even a fireplace).
It also depends on how tight the home is constructed. Make up air is essentially a hole in the wall - after we go through all this effort to make the home tight. Though more modern furnaces do have a more elegant solution.
Don't take this as professional advice but I think being in an open room does help. At a minimum, I would relocate the air input so it's not competing directly with the furnace draft. Preferably through the floor to the room above (outside would be even better - but I know it gets chilly in Detroit). If that's not feasible, then to as far away from the furnace as possible. That might mean an interior duct so that the intake is effectively opposite the sinks as you have planned.
Also, I would add a CO detector as you mentioned - if it goes off you'll need a plan B for ventilation. But I would put it in the room where the furnace is, but not too close. I would also put the fan on a timer, so that there is no chance of leaving it on overnight. Finally, I'd go with a less powerful fan - under 300cfm - or one with 2 speeds. CO will hurt you a lot more and a lot faster than darkroom chemical fumes.
Obviously the biggest danger is when people are asleep, especially on the same level as the furnace.