How long have you never seen the blue sky and white clouds.

Particle counter now very hot selling now because it can check air quality.
Do you know what is the quality of the air you breath everyday? does it health?
The air pollution is very bad in recent years.  how long you haven't seen the blue sky?
Laser particle counter can check the air quality around us and also demo air purifier.
It only need 35 seconds can know the air is good or not. very easy operate.