Abstract In view of the fact that the temperature of discharge from coal pulverizers was of interest because of the effect that it might have on the amount of air passing through the preheater, and on the amount of uncontrollable air through the furnace, data were taken in a number of plants covering temperature of air entering pulverizers, temperature of air in coal discharge, moisture of raw coal entering the pulverizer, moisture of discharged coal, and weight of coal pulverized per hour. Two sets of points were plotted, one showing the temperature of discharge for given entering temperatures, and the other the temperature drop through the pulverizer for given entering temperatures. In plotting the data no consideration was given to the size of pulverizer, amount of coal pulverized, or the moisture content of the coal. The plotted points fell in a straight band having a width of approximately 65 deg. A straight line drawn through the band shows the average variation within 35 deg. Sufficient information was obtained in the cases of two plants to calculate heat balances. From these heat balances leakage of uncontrolled air into the pulverizer was calculated. It was found that this amounted to about 2 per cent of the total air for combustion.