A heated humidifier including an autofeed mechanism disposed within a humidifier chamber. The autofeed mechanism includes a housing, a float, a stem, and a sealing body. The housing defines an inlet, an outlet, a first chamber connected to the inlet, and a second chamber connected to the outlet and the first chamber by a channel. The float moves within the second chamber with the stem projecting therefrom and through the channel. The sealing body is within the first chamber and cooperates with the stem. In an open state, the sealing body is displaced from the channel to permit filling of the humidifier chamber. In a closed state, the sealing body seals the channel to prevent liquid flow to the outlet. A location of the sealing body relative to the channel is controlled by the float as a function of a humidifier chamber liquid level.