Past: 

Jilin used to heat itself with an oven. Waste corn stalks are collected and dried in the fall, and then used as fuel in the winter. This method can guarantee the warmth of the room, but its disadvantages are obvious. First of all, corn stalks produce a lot of carbon dioxide when they are burned, which makes them vulnerable to carbon dioxide poisoning. Secondly, this burning behavior is very environmentally unfriendly. And there's a limit to how much heat you can create by keeping the temperature up. Humans need to do a lot of work in the system to keep it running.

Now: 

Central heating is now available in Jilin. This is a method of heating on a community basis. The coal is first delivered to the boiler rooms in each community, and then the coal is used to heat the water, delivering the extremely hot water to the radiator in each home. This method provides good temperature control and keeps the indoor temperature within a comfortable range. But the disadvantage is that individuals cannot control the indoor temperature and burning a lot of coal still leaves a lot of pollution.