I have an 8x8 ft furnace room with a 2x3 ft maintenance access door, plus an entry door. The room contains only the high efficiency furnace which has intake/exhaust pipes through the outside wall.
I have read that a grill is usually required for air circulation. Since I don't have that I keep the doors ajar, but would prefer not to.
Does this rule apply to rooms with a high efficiency furnace and no water heater?