Green’s Dictionary of Slang

air bubble n.

[‘the control room at Mount Eden Women’s prison (Auckland) is encased in a convex glass shell and resembles a large bubble’ Looser]

(N.Z. prison, also bubble (room)) a control room, usu. encased in transparent glass.

[NZ]D. Looser Boobslang [U. Canterbury D.Phil. thesis] 6/1: air bubble n. the Control Room, guard house [...] 32/1: bubble, the (also the bubble room) n. the prison officials' office, the Control Room, the guard room.