Removed old down-draft gas furnace in closet area and replaced with High Efficiency down-draft. Combustion air vented from outside as well as exhaust. Not a typical straight up through roof or chimney, but through a exterior wall. All the necessary ends for both feeds are in place. The question is before I replaced the old furnace, air vents across the top of furnace would supply the return air (combustion) and come from within the family room and make a considerable amount of noise from the sucking of air. On another wall, a bottom vent also existed. I'd like to drywall those areas over and have the furnace room from the Family room not have those vents on the wall. Access to the furnace room, where a hot water tank also resides is accomplished by going through a walk-in closet from the Master Bedroom. Oh yea, this situation was created by the addition of a wing to the original house. It has a crawl space, where the balance of the house has a basement. Subsequently I have 2 furnaces, 2 Hot water tanks and 2 Air conditioning units.
Also this furnace (down-draft) and in the basement a Up-draft, both use propane gas. They both have been operating rather well, but I'd like to clean up the walls in this family room area without causing any problems. Your answer would be appreciated

When you go to get your building permit to install your new furnace ask them OR follow the manufactures instructions. Codes are different in many of the states and I would not want to steer you wrong.