You have no idea what make up air in a utility room is for.

If your kitchen exhaust fan is running and your atmospheric vented appliance is also running, it can absolutely suck the CO exhaust right into the house. People have died from this - that's why on new builds, it's required by code to have a flue damper sensor so they know if the exhaust is being pulled into the home. OP may not have this. 99% of furnaces do not have the capability to detect CO or O2 levels.