In addition to the conditions of solitary confinement, one of the most sadistic and torturous methods that New York prison officials use against inmates is plexi-glass sheilds. These are transparent plexi-glass and are used to cover a prisoner's whole cell door so that he's incapable of breathing if the ventilation isn't functioning. The shields, coupled with the lack of space in a cell--48 square feet--works a hardship on inmates' health. In the company I'm in now, the CO's use plexi-glass shields for any minor thing: talking loud, indecent exposure and calling them names, among other things. This is how CO's control prisoners.
-- A New York Prisoner, July 2004