When PM2.5 under 10 means you are in safe air or not

PM2.5 means the fine particulate matters in the air under 2.5 μm. can go inside human body.
The WHO request the daily PM2.5 should under 10 μg/m³, what about your living place pm2.5 result?
Result under 10 is not means you are in safe. it is also have fine particulate matters when we breath.
Particle counter is the best device to check PM2.5 and PM10 result in the air.
It can also tell you how much 0.3μm in the air too which is more small particulates.