What is the purpose of furnace ventilation before the boiler starts?

　　The purpose of furnace ventilation is to discharge combustible gases and substances that may exist in the furnace and flue, and to discharge part of the ash on the heating surface. This is because when there are combustible substances in the furnace and combustible gas is precipitated from it, deflagration can occur at a certain concentration and temperature, causing a strong impact and damage the equipment; when there is dust on the heated surface, it will increase heat It affects heat exchange, reduces boiler efficiency, and even increases flue gas flow resistance. Therefore, the furnace and flue must be ventilated for 5 to 10 minutes with a rated air volume of about 40%.