Abstract: A humidifier having an ambient temperature sensor for sensing the temperature of the ambient air in the environment in which the humidifier is located. A difference temperature selector is provided to allow a user to select a difference temperature which is the difference in temperature between the sensed ambient temperature and a comfortable and efficient temperature for supply of the humidified gases provided by the humidifier to a patient or user. The humidifier controls the temperature of the humidified gases it provides to the patient to the selected difference temperature above the sensed ambient temperature, so that any change in the sensed ambient temperature results in a corresponding change in the temperature of humidified gases supplied to the patient or user. This construction prevents or minimises the condensation which occurs at low ambient temperatures in the gases supply conduit provided between the humidifier and the patient or user.

Abstract: An infrared gas analyser. The analyser comprises a sample cell located in a gas flow, a source of infrared radiation of selected wavelengths which is propagated through the sample cell and an infrared detector which receives radiation which has passed through the cell, The radiation incident on the detector provides a measure of the concentration of selected substances in the gas flow due to one of the wavelengths being selected to be absorbed by the gas being measured. One preferred use is as a humidity sensor in a medical respiratory circuit where at least one selected wavelength is a wavelength strongly absorbed by water. Heating means am associated with the sample cell to vaporize any liquid water which may enter it and the cell is provided with internal baffles to reduce deposition or condensation of water on internal surfaces through which infrared radiation must pass.