Possible Cause #1:
There is dust on the particle sensor lens
Solution:
Clean the particle sensor lens according to the user manual instructions (page 15)
Possible Cause #2:
Sensor sensitivity is too high (Pollution level is continuously high)
Solution:
Adjust the sensor sensitivity to a less sensitive level or standard level (user manual page 14)
Possible Cause #3:
Sensor sensitivity is too low (Pollution level is continuously low)
Solution:
Adjust the sensor sensitivity to a more sensitive level or standard level (user manual page 14)