Hello Beijingers, I'm selling my fantastic Blueair 503 air purifier in great condition. Blueair is a Swedish company and probably the best brand in terms of air purifiers. This model is one of their top class models, ideal for apartments up to 56sqm, with a powerful and quite silent purifying system. Original price is 6860rmb and I'm asking only 4000rmb for a purifier in brand new condition with roughly one year and a half use. I still have the date stamps and manuals. Please check the original price and specifications below: www.toranacleanair.com/AirCleanerModels.html If interested, please contact me.