The room can be accessed by side stairs jutting outside the exterior of the Bathhouse. Lin brings Kamaji his meals through a sliding door. Haku shows Chihiro Ogino the way through the Bathhouse by using Spirit Realm Magic.
Another access is above: Haku, transformed as the dragon Ryū, flies from Yubaba's bureau to the Boiler Room bypassing an abyss.
Most of the room is occupied by an imposing furnace. Its walls are lined with drawers containing herbs that Kamajī sends herbal-infused water up to the baths. Bath Tokens indicates the water and herbs that arrive at the destination bath.
The rest of the space is largely empty, save for a large wooden structure that acts as Kamajī's bed and workplace as well as the multiple holes in the wall that act as living space for the Sootballs. Kamaji keeps his personal stuff in the wooden structure for example a Sea Train ticket. Haku stays here as he recuperates from his magical injuries due to Kamajī's medicinal knowledge.
- The Art of Spirited Away, page 28