A measure of the rate of heat loss from the bulb of the kata thermometer. Although the cooling power as obtained by this instrument is not a measure of the capacity of an atmosphere to cool the human body, nevertheless, it is useful for comparing different atmospheres and provides a convenient index of the comfort condition of a working place in a mine. Experience indicates that a face will be reasonably comfortable for working if the dry kata cooling power is above 7 on the kata thermometer and the air velocity above 1 m/s.