Cryo chamber

A Cryo-chamber is a chamber that allows all UNSC nonessential personal to be frozen for long voyages. They are basically large metal pods with form fitting gel beds where the personnel are frozen until they are "needed". Master Chief makes his first appearance in Halo 1 inside a Cryo-chamber.

The cryo chambers are usually stored in their own areas of the ship. Each cryo chamber will hold an individual for as long as necessary, provided they use a Bronchial Surfactant, and can be ejected prior to a ship landing, thus saving some crew from harm to be recovered later. Linda-058, after being severely injured during the fall of Reach, was placed in a cryo chamber in the Pillar of Autumn. Prior to the ship's landing on Installation 04, her cryo chamber was ejected, and she was picked up by the Master Chief at a later date.

Cryo Chambers are monitored by the Ship's AI, and the AI can awaken crew members at a moments notice. Cryo wake-up protocols demand that crew check each other to make sure everyone revives from cryo alright. There is usually a medical pod in cryogenics bays for emergency resuscitations. Many times people are stored in cryo pods naked, as covered skin generally reacts badly to the cryo process, leaving skin raw and blistered.

However, in Halo: Combat Evolved, the Master Chief emerges from the cryo pod completely fitted in his armor, using Spartan training to ignore the pain. His enhanced physiology presumably allows for a quick recovery from superficial injuries such as this.

Trivia

 * Cryo-chambers are refered to as "the freezer" in slang.