Jimmy - an inmate who arrived with Alex, Zee and Monty. Ended up sabotaging the main escape plan of the story by calling on guards as Alex, Zee, Toby and Gary fled into Room 2. Status unknown; presumed dead.
Toby Merchant - a very young inmate who arrived with Ashley and Gary. Was originally going to commit suicide with Ashley, but was dissuaded and became part of the main escape plan. In the explosion in Room Two Toby was badly injured, but begged Alex to jump into the river anyway. In Solitary, Zee confirms Toby never resurfaced and died in the river.
Ashley Garett - an inmate who arrived who arrived with Toby and Gary. Tried to commit suicide with Toby, refusing to do so alone. Killed by Alex.
Carlton Jones - Zee's cellmate. Status unknown.
Adam - Donovan's former cellmate, was taken by the bloodwatch and left the five scratched in marks on his cell wall. Status unknown; presumed dead.
Ozzie - an inmate who'd escaped the infirmary and lived with Pete and Simon under genpop. Is killed by Alex in one of Alex's trials in becoming a blacksuit.
Scott White - the first inmate to perform a legitimate escape attempt in Furnace. His plan was to crawl through the then existing air vents and onto the elevator up. Nearly made it but was caught by blacksuits and was executed by the warden's dogs back in genpop.
Oli - an inmate from the Furnace short stories best known for being a terrible barber. Status unknown.
Pete - Former Skull gangster, had been taken in during the Summer of Slaughter. Had become a rat in the infirmary and lived with Simon and Ozzie. At the end of Solitary he stayed behind with Ozzie as Alex and Simon started climbing the incinerator, but is presumed dead in Death Sentence when the tunnel he is hidden in is blocked off by Cross.