Diagnosis
The laser particle sensor is contaminated or obstructed. Dust accumulation causes inaccurate readings, defaulting to the 'good' indicator.
How to Fix It
Clean the sensor. Power off the unit. Locate the sensor inlet on the rear panel. Use a can of compressed air to blow dust out of the sensor chamber. Gently wipe the external sensor grill with a dry cotton swab. Allow a minute for any dislodged dust to settle before powering on.
If That Didn't Work
The unit may be in a poor location for sensing. Ensure it is at least 6 inches away from walls, furniture, and corners. Avoid placing it directly under an air vent or in a dead-air space. Relocate the purifier to a central, open area and monitor for 24 hours.
Heads Up
Sensor calibration occurs automatically on power-up. After cleaning, run the unit on high speed for 15 minutes to allow the sensor to recalibrate. The light should begin responding to air changes.