jd.com or taobao for an affordable 399RMB. It is very beautifully designed product, aimed, as part of their smart living concept, at being used in conjunction with smart air conditioner.
It *claims* to be able to detect and measure both Volatile Organic Compound (VOC, i.e Ozone), as well as the famous small PM2.5 particulate matter. But can it really do so? To know the answer, check our latest on-going experiment about the Air Box at experiments/haier-air-box