The Furnace Room is the first room seen when walking through the Cellar Door. The name is based on the object to the right of the stairs; a black square with a black pipe rising out of it, which oscillates left and right.
The room itself is comprised mostly of a brown, dirt-like texture. Sounds in this room have a slight echo to them, like many rooms in this area. The room is mostly rectangular, with a small alcove coming off of the bottom-right corner.
The center-top of the room is dominated by stairs leading up to Cellar Door. To the left of the stairs, in the upper-left corner of the room, is a square group of 4.
On the left wall is an opening leading to the Office Hallway.
To the right of the stairs is the titular furnace (or furnace-like thing), a black object that moves back and forth slightly, with a pipe coming out the top. Its actual purpose and function are unknown.
In the bottom right of the room is another alcove, with another square group of 4. There are various framed images of the wall, though it's difficult to make anything out — only that there are two pictures of something circular, and then three copies of another picture.