Factory Calibration & Lifetime Limitations
PurpleAir sensors use Plantower laser counters that are factory-calibrated before shipping. There is no method for post-production calibration of the laser counters—you can’t adjust or calibrate the sensor yourself.
What You Can Do to Maintain Accuracy
Although calibration isn’t possible, you can help ensure accurate readings through proper maintenance:
- If one channel is stuck at zero, spikes, or shows errors, it may be clogged with dust, debris, or even insects.
- Safely clean the intake holes with compressed air or a shop vacuum, following the Sensor Maintenance Guide and video tutorials. Be sure to power off the sensor before cleaning and avoid spraying air directly into the fan
- Laser counters typically last about 2 years, although environmental factors (humidity, dust, heat) can shorten that lifespan
- If cleaning doesn’t resolve performance issues, replacement is the recommended solution.
Managing Temperature & Humidity Sensors
- The temperature and humidity sensors in your device are also factory-calibrated and cannot be recalibrated post-production
- Look for mapped corrections in the PurpleAir interface (e.g., “Temperature °C” layer), or note firmware-affected readings—older firmware like v7.04 may skew temperature slightly
Calibrating Temperature sensors
External Calibration & Alternative Algorithms
While you can’t calibrate the sensor hardware itself, you can apply external correction algorithms to data:
- PurpleAir offers alternative conversion methods for PM2.5 readings, such as ALT-CF3.4, which have been validated against reference monitors and offer improved precision and lower detection limits compared to the default CF=1 method Calibration of PurpleAir monitors
- Users can select these conversions in the PurpleAir map or API, allowing for better comparability with regulatory-grade data.
Performance Over Time
Long-term studies show that sensors degrade gradually:
- After 4 years, the average disagreement between a sensor’s two channels increases by ~4%, and approximately 2% of sensors experience permanent degradation Sensor Owner’s Guide
- Sensors in hot/humid climates may degrade faster—regular monitoring and maintenance are key.
Troubleshooting & Support
- For detailed cleaning procedures and step-by-step video guides, check the Sensor Maintenance Guide
- For help choosing the right data conversion method, see the PurpleAir map help or API documentation.
- If issues persist after cleaning or replacing parts, feel free to reach out to us for support.
Learn More
Learn more about sensor maintenance.
Learn more about how the sensors function.
Learn more about how we measure air quality.