Abstract: A heater and humidifier for use with a breathing mask or other breathing apparatus, to avoid unpleasant and injurious effects of prolonged breathing of cold dry air, or other breathing gas mixture. The action is accomplished by injection and combustion of hydrogen directly in the breathing gas, and is carried out in a safe manner adjacent to or in the breathing mask. In addition to the heating effect, the hydrogen combines with oxygen in the breathing gas to produce moisture. The apparatus is adaptable to use under water, or in the atmosphere at any altitude and can be operated without a special power source.