Employees demand cleaner office air

It's not only about salaries, promotions and career prospects - many companies in China have found they need to offer cleaner air inside their offices to lure and retain staff.

Air quality has deteriorated badly in China's north and east, including in Beijing and Shanghai. Companies based in these cities, especially multinationals, are spending tens of thousands of dollars to install air filtration systems and real-time pollution monitoring devices in their offices.

International market research company J.D. Power has installed new clean air systems at its Beijing and Shanghai offices, an executive said. Auditing firm PricewaterhouseCoopers and British advertising firm WPP are doing the same.