There are multiple reasons why a sensor could be reading higher. The sensor may be experiencing a hyper-local event, causing its readings to be temporarily higher. Smoking and cooking are two common examples.
If the sensor’s readings are consistently high, you’ll first want to check its placement. Is there anything near the sensor that could be a consistent source of particulates? You can try moving it to a new location and see if the readings change.
If you’re confident the sensor placement isn’t the cause, you’ll want to try cleaning your sensor. Insects or debris can get inside the laser counters, causing readings to become high, and cleaning can sometimes resolve this. If cleaning doesn’t work, you can purchase replacement laser counters for your device.