Texas Local Government Code - LOC GOV'T § 351.009. Safety Vestibule

(a) To provide safety to officers and security, entrance to and exit from a cell block or a group of cells or compartments used to confine three or more prisoners in a county jail must be through a safety vestibule.

(b) A safety vestibule must have one or more interior doors in addition to the main outside entrance door to the cell block or group of cells or compartments. All the interior doors must be designed to be locked, unlocked, opened, and closed by a means located outside the cell block or group of cells or compartments.