A method for turning off fluid flow through a valve. The method includes: movably disposing a member in an interior of a housing between a first position in which an inlet and an outlet are in fluid communication with each other and a second position blocking the fluid flow; restraining the member in the first position when a fluid temperature in the interior or an ambient temperature outside the housing is below a threshold temperature; and releasing the restraint such that the member is capable of moving to the second position when the fluid temperature or the ambient temperature is above the threshold temperature; wherein the releasing comprises changing the shape of an actuator from a first shape restraining the member to a second shape releasing the restraint upon a change in the fluid temperature or the ambient temperature from below the threshold temperature to above the threshold temperature.