A mechanical latch assembly includes a supporting frame, a locking latch, an actuation arrangement and a safety lock arrangement. The locking latch is slidably mounted on said supporting frame in longitudinally movable manner. The actuation arrangement includes an actuation handle pivotally connected to said supporting frame to longitudinally drive said locking latch moving between a locked position an unlocked position. Moreover, the safety lock arrangement includes a locker member movably mounted on said supporting frame, wherein said locker member has a slider slot formed thereon to define a pusher surface and an opposed retracting surface, and a thermal activated arm substantially extended from said supporting frame to slidably pass through said slider slot of said locker member at a safety temperature, and adapted to deflect to push said locker member at said pusher surface at an elevated operation temperature.