A system of locking a door is disclosed. The system according to the present invention comprises a releasable keeper that secures a door locking mechanism to keep a door secured to an enclosure in a locked position. A release mechanism that is operated from the interior of the enclosure releases the releasable keeper from the enclosure and enable the door to be opened and prevents people from becoming trapped within the enclosure by a locked door. In an exemplary embodiment, the release mechanism is operated by a lever that operates a pulley system to disengage the release mechanism from the releasable keeper.