Few Shanghai enterprises are aware of the potential health hazards posed by centralized air conditioners, and fewer still have cleaned their systems in recent years, an official from a municipal health organ said.

The Shanghai municipal health inspection bureau has conducted many random inspections of centralized air conditioners this year, and "the results were very disappointing," said Zhou Yanqing, vice-director of the bureau.

"Less than 20 percent of air conditioners inspected had been cleaned at least once, and most of the rest had never been cleaned," Zhou added.

Zhang Zheng, manager of Eslon Environmental Engineering Co Ltd, made similar comments. Elson offers air-conditioner cleaning services.

Zhang said more than 10,000 buildings were equipped with centralized air conditioners.

"But less than 5 percent of them clean their air conditioning systems regularly," he said.

Zhang cited Lippo Square, a commercial building on Middle Huaihai Road, as an example. The building opened for business at the end of 1999, but only recently cleaned its air-conditioning system.

It took 15 cleaners and three cleaning robots 24 days to clean out the 43-story building's air-conditioning system.

The cleaners collected 500 kg of rubbish, including dust, debris, building materials and even dead mice. The effort cost the building's managers hundreds of thousands of yuan.

"In fact, Lippo is not the only building on this busy street that needs to clean its air-conditioning system. I think some buildings have not even thought about cleaning their systems yet," said Zhang.

A regulation issued by the Ministry of Health in 2003 requires building operators to thoroughly clean the ventilation systems of their centralized air conditioners at least once every two years.

"The high cost of cleaning and lack of awareness of the health problems caused by polluted air are the two main reasons that so few systems are cleaned regularly," said Wu Shida, an official from the Shanghai municipal disease control and prevention center.

Many disease-causing bacteria, including Legionella, which was thought to be culprit behind the SARS outbreak of 2003, have been found in the thick dust lining the pipes of many air conditioners, Wu said.

"It is necessary to inform enterprises of the importance of cleaning their air conditioners on regular basis," said Zhou. "And the local government needs to do something to strengthen punishments and standardize the work of air-conditioning cleaning companies."

Shanghai is currently carrying out a legislative survey that could lead to the drafting of a regulation on the hygiene of centralized air conditioners in public buildings. Zhou's bureau is responsible for collecting public opinions on a possible regulation.

(China Daily July 24, 2007)