A heater can be configured to operate with either a first fuel at a first pressure or a second fuel at a second pressure and can include a fluid flow controller. In some embodiments, the fluid flow controller is configured to permit flow of fuel to a first passageway and to direct a first fuel to a first oxygen depletion sensor line when the controller is in a first position and permit the flow of fuel to a second passageway and to direct a second fuel to a second oxygen depletion sensor line when the controller is in a second position.