A gas spring (10; 10') for forming equipment, comprising: a casing including an axially extending side wall with an interior surface, an open end, a transversely extending closed end wall axially spaced from the open end, and a pressure chamber established in part by the side and closed end walls to receive a gas under pressure therein; a piston rod housing (44; 44') including an inner end and an outer end axially spaced from the inner end and the piston rod housing (44; 44') is received in the casing adjacent the open end of the casing; a piston rod extending through the piston rod housing (44; 44') and having an inner end received in the pressure chamber and an outer end normally outside of the casing; and characterized by a piston rod seal encircling and bearing on the piston rod, including an inner lip in sealing engagement with the piston rod and an outer lip in sealing engagement with one of the piston rod housing (44; 44') or the casing and providing a seal between the piston rod and the one of such casing or piston rod housing (44; 44'); an overtravel pressure relief collar slidably received around the piston rod and having a collar outer end that projects axially beyond the open end of the casing and a collar inner end configured to contact at least a portion of the piston rod seal so that generally during an overtravel condition of the piston rod, axial movement of the collar toward the closed end of the casing displaces at least part of the piston rod seal from the piston rod to provide a path for escape of a gas under pressure from the pressure chamber to the exterior of the gas spring (10; 10'). a casing including an axially extending side wall with an interior surface, an open end, a transversely extending closed end wall axially spaced from the open end, and a pressure chamber established in part by the side and closed end walls to receive a gas under pressure therein; a piston rod housing (44; 44') including an inner end and an outer end axially spaced from the inner end and the piston rod housing (44; 44') is received in the casing adjacent the open end of the casing; a piston rod extending through the piston rod housing (44; 44') and having an inner end received in the pressure chamber and an outer end normally outside of the casing; and characterized by a piston rod seal encircling and bearing on the piston rod, including an inner lip in sealing engagement with the piston rod and an outer lip in sealing engagement with one of the piston rod housing (44; 44') or the casing and providing a seal between the piston rod and the one of such casing or piston rod housing (44; 44'); an overtravel pressure relief collar slidably received around the piston rod and having a collar outer end that projects axially beyond the open end of the casing and a collar inner end configured to contact at least a portion of the piston rod seal so that generally during an overtravel condition of the piston rod, axial movement of the collar toward the closed end of the casing displaces at least part of the piston rod seal from the piston rod to provide a path for escape of a gas under pressure from the pressure chamber to the exterior of the gas spring (10; 10').