The purpose of the chair is to be sat on. This will satisfy a prisoner's or staff's Comfort need.
Chairs are compulsory in Offices, Receptions and Security rooms. They are used by prisoner during Alcoholics Group or Behavioural Therapy reform programs, and they can be used instead of Benches (you still need one bench) in the Canteen. Up to 10 chairs fit around one Table (4 on each long side, 1 on the short ones). You can replace chair in most of the rooms where chair is required with objects such as Wooden Stool or Office Chair.