There are two main advantages of having two sensors:
a) Data quality: You can detect if one sensor fails as the two readings will start to deviate and then replace the faulty one
b) Extend the life of the monitor: The PM sensors with the laser and optics have a limited life. By having two inside, you can alternate the measurement and put them in sleep mode inbetween. Thus extending the life of the monitor.
Just a note: can you stagger the sensor time a bit unevenly?
Instead of 50%/50% time split, can you do something like 40%/60%? This reduces the risk of both sensors failing at once because they have approximately the same duty time.
The failure modes are commonly fairly apparent. One sensor will go to a static low value and the other will show normal variability.
In the theoretical limit of all mathematically possible failure modes and all possible environmental conditions, this would be impossible of course. But we live in a fairly predictable environment and the nature of the failures is not unlimited. As such, it is pragmatically pretty easy to see the difference.
a) Data quality: You can detect if one sensor fails as the two readings will start to deviate and then replace the faulty one
b) Extend the life of the monitor: The PM sensors with the laser and optics have a limited life. By having two inside, you can alternate the measurement and put them in sleep mode inbetween. Thus extending the life of the monitor.