Resetting G7 EXO Pellistor (Catalytic Bead) LEL Sensors after an Overlimit Exposure

Background

High concentrations of combustible gases affect pellistor (catalytic bead) Lower Explosive Limit (LEL) sensors in ways that do not apply to Infrared (IR) or Molecular Property Spectrometer (MPS) LEL sensors.

If a pellistor (catalytic bead) LEL sensor is exposed to Overlimit (OL) concentrations of combustible gas (e.g., 200% LEL CH₄) for more than a few seconds, the sensor behaviour may be impacted in the following ways:

• The sensor may display a significant shift off of the baseline zero value and record a %LEL value for the combustible gas, even in fresh air.
• The sensor may lose sensitivity and be unable to accurately measure the %LEL value for the gas.
• The sensor catalytic beads may be permanently damaged, and the sensor will no longer be able to detect gas.

NOTE: IR and MPS sensors cannot be damaged or poisoned by OL LEL gases.

Resetting G7 EXO Devices after an OL Exposure

IMPORTANT: In the event of an OL exposure, G7 EXO devices equipped with pellistor (catalytic bead) sensors will shut down and remain in an OL alert state until they are manually reset.

To reset G7 EXO devices equipped with pellistor (catalytic bead) LEL sensors that were shut down in an OL alert state:

1. In a known clean environment, power on the device.
2. After the device is restarted, perform a bump test and calibration to ensure that the sensor is fully functional.

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