Hi, I have two Blueair purifiers for sell. Both have automatic sensors and come with remote controls.

The IR sensors are used to filter out dust particles, smoke and smell. They also have a built in filter change meter.

I got them end of last year and they are still as good as new since I hardly used them. Filter's were changed 3months ago.

The 550e model can filter out up to 60sqm. Selling for 3800rmb (bought for 6000)
The 450e model can filter out up to 45sqm. Selling for 3000rmb (bought for 5200)