Concerns are again being raised over the widespread use of unsafe coal and gas boilers after at least 10 people died in Beijing this week from suspected carbon monoxide poisoning, state media reported  on Wednesday.
Neighbours found five university students unconscious in a rented flat in the city’s Chaoyang district on Monday.The students were rushed to Chaoyang Hospital emergency department but were reported dead on arrival.
Doctors said at least three of the students were victims of carbon monoxide poisoning from fumes released from a punctured gas water heater in their bathroom.
The Harbin Medical University students were working as interns at the China-Japan Friendship Hospital.
In the same district on Tuesday, a family of five, including a seven-year-old boy, was found dead from suspected carbon monoxide poisoning. Neighbours said a coal heater was installed in a corner of their apartment and investigators found a carbon monoxide detector unplugged.
Police are investigating both cases.
According to official statistics , about 17,000 old-style “vertical gas boilers” are still being used in the city despite being banned by the government in 1999. In 2011, 38 people died from carbon monoxide poisoning.
In a bid to curb carbon emissions and tackle the city’s pressing air pollution problems, Beijing officials are looking to phase out old coal-fired heating systems, which are still being used in more than 44,000  homes in the city. A pledge was made last year to replace all coal-fired equipment in Beijing's core areas by the end of 2013.
Many residents living in poorer or rural areas still use coal boilers to keep warm during harsh Beijing winters that can see temperatures drop as low as minus 15 degrees Celsius.