Have a look at this story :
https://www.thethingsnetwork.org/labs/story/reporting-pm25-pm10-micro-particle-dust-sensor-by-using-arduino-and-lorawan-atim-acw-duino-shield
Building a micro particle LoRaWAN sensor
Have a look at this story :
https://www.thethingsnetwork.org/labs/story/reporting-pm25-pm10-micro-particle-dust-sensor-by-using-arduino-and-lorawan-atim-acw-duino-shield