Abstract: A calorimeter which measures a naturally induced flow of incoming air in a horizontal entry duct (air-inlet chamber) and through a horizontal elbow duct to an upright straight flue used as a combustion chamber, the measuring system consisting of a thermistor version of a hot-wire anemometer, a bridge circuit with a matched thermistor, and a strip chart recorder, the calorimeter utilizing convective air flow to make practical a method for directly, continuously, and quantitatively measuring, over the entire period of combustion from ignition to extinguishment, the heat emitted by a burning test material positioned in the upright vertical flue, thus providing a realistic, sensitive, and accurate method for monitoring quantities such as the total heat emitted per unit mass of sample, the total heat emitted per unit mass of volatilized portion, the maximum emitted energy flux, and the average burning acceleration, the apparatus being particularly useful for continuously evaluating burning behavior, particularly o