DIAGNOSIS Dust, pet dander, or oils have clogged the small laser-based PM2.5 sensor inlet on the top edge of the thermostat, causing false high readings.
FIX Physically clean the sensor slot.
- Power down your HVAC system at the breaker.
- Gently pull the display off the wall plate.
- Use a can of compressed air (held upright) to give several short bursts directly into the thin horizontal grille on the TOP EDGE of the display.
- Use a dry, clean makeup brush or soft-bristled electronics brush to gently dislodge any visible dust from the grille.
- Reattach and restore power. Allow 30 minutes for new readings.
IF THAT DIDN'T WORK The sensor may need recalibration. Go to the thermostat, select the air quality icon, and choose 'Calibrate Sensor'. Follow the on-screen instructions, which involve leaving a window open for a period. This resets its baseline.
HEADS UP Never use water, cleaning sprays, or vacuum cleaner attachments. You'll destroy the sensitive laser and mirror inside. The sensor is designed for ambient air, not right next to a burning candle, kitchen stove, or humidifier.