legal, yes

Coal gas is a gas containing combustible components made from coal. According to the processing method, gas properties and uses, it can be divided into: water gas, semi-water gas and air gas (or producer gas) are obtained from coal gasification.

these gases have low calorific value, so they are collectively called low calorific value gases; The gas obtained by coking in coal dry distillation is called coke oven gas.

belongs to medium calorific value gas, which can be used as civil fuel in cities. Carbon monoxide and hydrogen in coal gas are important chemical raw materials.