It displayi Pm2.5 cum tor: Display screen (a real time value) Grade display Good, and poor and poor. With every change The grade of air qualitative, liqht changes its value. Gaseous state torrents Not only pm2.5 differential The atmostphere can be also detemine Grade display The possibility of the air through, Good, and poor and poor. With every change The grade of air qualitative, light intensity changes. Filter life indicator Two times, the life/service of pre filter And it 's an example filterer. Basis this Filter or replacement.