Hard choice: winter heating or clean air?

An elderly man exercises on the side of Songhua River in the heavily polluted city of Jilin, Jilin province, on Feb 24. Heng Guoliang / For China Daily

Winter in northern China is much colder and longer than in the South. That's why cities in northern China receive 24-hour heating dail, usually between the months of November and March.

The central heating system in China is mostly coal-based which is technically inefficient compared to electric, gas and oil heating systems in many western countries.

The north of China comprises 17 provinces, municipalities and autonomous regions. It has a population of more than 700 million, almost the same as all of Europe. It accounts for about 60 percent of the country's territory.

The energy needed to run the systems here costs about 70 billion yuan. But due to the inefficient heating systems, about one-third of that money is wasted. In the south, household-based heating supply systems have been introduced in some places to better save energy and protect the environment.