Abstract: A liquid level sensing device, particularly useful for apparatus designed to humidify oxygen gas being administered to patients undergoing respiratory therapy is disclosed. The liquid level sensing device detects the liquid level in a canister having an optical probe therein. A bracket, rotatable on a frame of the device, carries a light source and a light sensing member for determining liquid level in the canister in conjunction with the probe. The hinged bracket engaging relation, and it also rotates out of probe-engaging relation and registry with the light probe. When the bracket is out of registry with the light probe, the canister may be removed and replaced. The bracket may be releasably retained out of probe-engaging relation by means of a snap fit structure.

Abstract: Improvements are disclosed in liquid level sensing apparatus having a liquid replenishment line so that as liquid is expended more may be added to keep the liquid at a desired predetermined level. The apparatus is contemplated for use in the humidification of gases, particularly for the administration of oxygen and the like to a patient.