The panic room, or safe room, is a room connected to a house or other location that can be secured upon entry. They are typically used in case of a break-in or home invasion, but also can be used for refuge from natural disasters like tornadoes and hurricanes.
At the Flynn-Fletcher house, the entrance to the panic room is located inside a crate in the basement. A ladder leads down to the panic room. The room itself is sparse and metal-lined. For unknown reason, cell phones can be used there, even though it would undoubtedly be out of range. The only decoration appears to be a framed needlepoint canvas that says, "The Panic Room". The Panic Room is apparently used merely as a safe haven for when one family member needs to calm down.
To date, Candace is the only member of the family known to use the panic room. For a while, she kept her stuffed bear, Mr. Miggins, in the room, and discussed strategy with him on how to capture one of the robots that had frightened her a few minutes before. ("I, Brobot," when she has a short nervous breakdown)