Customers using a pellistor (catalytic bead) cartridge may experience a negative baseline reading upon starting up EXO. This may show as a negative Under Limit (UL).
If a sensor has drifted too far into the negatives, it will trigger an Under Limit (UL) alarm on EXO.
NOTE: Mute the alarm by pressing and holding the up and down arrow buttons.
Before zeroing the sensors, make sure you are in a clean atmosphere with no ambient gas levels.
NOTE: If you are unable to move EXO (example: if the device is mounted to a wall), a trained technician should zero the sensors using a cylinder of clean air.