This test method is based on the loss in weight of a coal sample in an air atmosphere under rigidly controlled conditions of temperature, time, and airflow.a provision for renewing the preheated air in the oven at the rate of one to four times a minute, with the dry air.an exhaust change-over valve allows the output flow meter to be by-passed during operation, preventing the build of condensation in the flow meter.temperature range : above ambient to 150c 2c.timer provided to set the operation time.230 v, 50 hz. Power supply.