Abstract: There is provided a frame assembly 200 adapted for installation in a filter housing of an air handling system. The frame assembly is arranged having a frame 210 which is adapted to receive a filter unit of a predetermined size. The frame assembly further comprises a clamping mechanism 230 arrange for clamping the filter unit. An actuator 231 of the clamping mechanism is arranged at a front member 211 of the frame and is operable between an open and a closed position while activating the clamping mechanism to clamp the filter unit. An actuator element 232 facing a back member 212 of the frame is arranged such that a free distance between the actuator element and the back member during operation of the actuator corresponds to the predetermined filter unit size, thereby enabling operation of the actuator only if an inserted filter unit abuts the back member of the frame.