How clean indoor air is becoming China's latest luxury must-have

Shanghai’s latest upscale hotel boasts filtered air typically 10 times cleaner than that outside and in-room pollution monitors – but in this lucrative new market, not everyone can be trustedThe newly opened luxury Cordis hotel looks much like many other high-end hotels in Shanghai, with its glass-sided swimming pool, vast twin ballrooms and upscale spa. But the first Cordis hotel on mainland China boasts something that is genuinely rare in big Chinese cities: clean indoor air.Modest