UEi Test Instruments THL2 - Manual (Page 11)

Sensor Reconditioning
Over time, the internal sensor may be compromised as a result of
pollutants, chemical vapors, and other environmental conditions which
can lead to inaccurate readings. To recondition the internal sensor, please
follow the procedure below:
Dry the logger at 176˚F (80˚C) at <5% RH for 36 hours followed by
70˚ - 90˚F (20˚ - 30˚C) at >74% RH for 48 hours (for re-hydration).
If permanent damage to the internal sensor is suspected, replace the
Logger immediately to ensure accurate readings.
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