Troubleshooting the alarm when PM2.5 mass concentration is stuck to zero

The alarm is raised when 100% of the raw PM2.5 mass concentration readings acquired in the last 24-hour period are reporting zero µg/m³. The presence of this alarm might indicate a fan or laser diode malfunction.

note

If a Calibration is applied to the Node, you might see values different from zero on Dashboard charts even when this alarm is triggered. To verify the problem, plot the Node's raw PM2.5 mass concentration on the Historical Data page and turn on the Show Raw toggle — if the raw line sits flat at zero across the last 24 hours, the alarm is confirmed.

Troubleshooting the Node

Once you've confirmed the raw PM2.5 mass concentration is stuck at zero, please perform the following steps:

• Ensure the Node is properly deployed outdoors and exposed to ambient PM2.5 levels.

  • Constant zero readings are rare but possible. If the Node is in an area with exceptionally clean air, try moving it to a different location to check for a false alarm.

• Power cycle the Node:

  • Unplug and replug the solar panel or power adapter.
  • After the Connection Successful sound, listen for a faint fan noise by placing your ear near the Node's air inlet or outlet (black knobs at the bottom). Do this in a quiet environment.

• If you don't hear the fan:

  • The fan may be stuck due to debris. Follow these steps to clear any blockage.

• If the raw PM2.5 mass concentration remains at zero after these steps, please contact our Support team for a replacement.

What's next

• Clean the Node-S airways for erratic PM2.5.
• Troubleshoot the PM2.5 above-expected-bound alarm.
• Understand common device status alarms.
• Explore the device Diagnostics view.