# Do sensors decline in accuracy
**URL:** https://community.purpleair.com/t/do-sensors-decline-in-accuracy/22468
**Category:** Sensors
**Created:** [December 20, 2025, 11:07am UTC](https://community.purpleair.com/t/do-sensors-decline-in-accuracy/22468 "2025-12-20T11:07:12Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@PhilipLeith](https://community.purpleair.com/u/PhilipLeith)
#### Post date: [December 20, 2025, 11:07am UTC](https://community.purpleair.com/t/do-sensors-decline-in-accuracy/22468/1 "2025-12-20T11:07:12Z")
After a couple of years, I am getting much lower readings than I would expect. How do I know that it is the sensor failing or the environment changing?
---
### Author:  [@geo-allen](https://community.purpleair.com/u/geo-allen)
#### Post date: [December 24, 2025, 6:43pm UTC](https://community.purpleair.com/t/do-sensors-decline-in-accuracy/22468/2 "2025-12-24T18:43:02Z")
Sensors don’t usually slowly decline - they fail suddenly. If the A and B sensor data agree well, then it’s working. Failures are often debris that can be blown out with canned air. Sometimes a fan will fail. PAs can last 5 year or more - not always but there’s nothing that has a lifetime of a year or 2.
---
### Author:  [@PhilipLeith](https://community.purpleair.com/u/PhilipLeith)
#### Post date: [December 24, 2025, 7:18pm UTC](https://community.purpleair.com/t/do-sensors-decline-in-accuracy/22468/3 "2025-12-24T19:18:43Z")
Thanks. It is a gonner, I think. I have been measuring PM2.5 from a restaurant below me and the restaurant is still there, but the readings are way, way down. You can see the paper I wrote on this site. Under Research. [Domestic indoor air quality arising from commercial cooking sources](https://community.purpleair.com/t/domestic-indoor-air-quality-arising-from-commercial-cooking-sources/22004)
I will take if off air.