A fire suppression apparatus that includes a housing defining a first chamber containing a gas generant. The apparatus further includes an initiator operatively associated with the first chamber and in reaction initiating communication with the gas generant. The initiator, upon actuation, acts to ignite at least some of the gas generant to form gas. The housing further defines a second chamber adjacently disposed to the first chamber. The second chamber contains an endothermically-alterable material and a piston assembly including a piston. Upon actuation, the piston moves to expel at least a portion of the endothermically-alterable material from the second chamber such that the expelled endothermically-alterable material contacts and cools gas formed by the ignition of the gas generant. The housing further has at least one discharge opening to permit cooled gas to exit the housing. Corresponding or associated methods for suppressing a fire are also provided.