This vent in our laundry/mudroom has two huge openings and vents directly outside (pictures linked at the end). When we bought the house, both openings were covered with a plastic film. During our inspection, it was recommended that we remove the plastic to provide airflow to this room, because our water heater and furnace are located in this room. So we did. But now it's been getting down to -15F at night, and I'm second guessing the decision to remove the coverings. The water heater and furnace have their own combustion pipes venting out. In that case, are these necessary? Are they old vents from a previous set up? Could I perhaps cover and keep a carbon monoxide detector in this room to monitor? Pictures: https://imgur.com/a/Yh3ckKd

This vent in our laundry/mudroom has two huge openings and vents directly outside (pictures linked at the end). When we bought the house, both openings were covered with a plastic film. During our inspection, it was recommended that we remove the plastic to provide airflow to this room, because our water heater and furnace are located in this room. So we did. But now it's been getting down to -15F at night, and I'm second guessing the decision to remove the coverings. The water heater and furnace have their own combustion pipes venting out. In that case, are these necessary? Are they old vents from a previous set up? Could I perhaps cover and keep a carbon monoxide detector in this room to monitor?