This piece is done during the “Hack for Air” Beijing Hackathon event and was done within 48 hours as a prototype of the whole project. We utilized the solenoid as an “Aerometer” detecting the level of PM2.5 level in the mega-city Beijing. All the solenoids are mounted on the foldable and manipulatable lamp arms. The knocking sounds produced by solenoid corresponded to the PM2.5 values monitored by the script running on mac. The whole structure attempts to mimicry a mechanic arm signifying the physical ecology outside.