Abstract: Control apparatus for preventing inadvertent operation of the drawworks of a drilling rig upon closure of an associated blowout preventer, the drawworks being at least partially operated by air from an air source connected thereto by an air conduit. The control apparatus may comprise control components for connection to the air conduit and movable from a first mode, in which air is permitted to communicate with the drawworks through the air conduit, and a second mode, in which air is prevented from communicating with the drawworks. Also included are monitor components for connection to the blowout preventer and the control components for sensing whether the blowout preventer is in opened or closed positions and initiating movement of the control components to the second mode upon movement of the blowout preventer to the closed position.