1) The sample in the porcelain boat should be flattened and the thickness of the sample should not be too large;

(2) When ashing, the furnace door can be opened, and the porcelain boat containing the sample on the heat-resistant plate can be slowly pushed into the mouth of the box shaped high-temperature electric furnace. First, the sample in the porcelain boat can be slowly ashing and smoking. After a few minutes, when the sample no longer smokes, slowly push the porcelain boat into the hot part of the high-temperature furnace, close the furnace door, and burn the sample at 815 ± 15. If a coal sample catches fire and explodes during the ashing process, the coal sample will be invalidated and must be re weighed for ashing.

(3) A warm furnace should have a chimney or ventilation hole to allow the coal sample to be discharged from combustion products and maintain air circulation during the burning process.

(4) The control system of the high-temperature furnace must indicate accurately. The temperature rise capacity of the high-temperature furnace must meet the requirements for measuring ash content.

(5) The ashing time should ensure complete ashing of the sample at a temperature of 815 ± 15, but arbitrarily extending the ashing time is also detrimental.