The PurpleAir PA-II sensor is very reliable. Three years ago we deployed 25 sensors throughout our region and they are all still running strong with high confidence.
I ordered a sensor last year to get accurate air quality readings in my neighborhood. The sensor works GREAT, customer service is GREAT, and I have no complaints. Highly recommend this product and company.
Brilliant company, responsive to customers' needs. The sensors are an excellent product and are gaining many fans in New Zealand.