Bad things some time happen to the best of humidity sensors. In its standard environment, the ChipCap device by General Eastern, a Div of General Electric will operate indefinitely. However, by the very nature of the device, the Chipcap is monitoring temperature and humidity. Sometimes this means that by accident or design, the sensor will be exposed to extreme temperature or prolonged expose to 100 RH or a low humidity. As the technology used to manufacture the capacitive sensor is a custom polymer, these extremes will cause the sensor to fail or yield incorrect outputs. However, there are a few things you can do to see if the sensor can be salvaged after being exposed to extreme elements.
Before starting any of these steps, make sure that the sensor has no power applied.
1. After being exposed to a condensing environment, the ChipCap sensor needs to be dry baked for one hour at 125°C (~0% RH), then exposed to 70% RH for 2-3 hours to rehydrate.
2. After being exposed to a high-temperature dry environment just rehydrate at 70% RH for 2-3 hours.
3. After being exposed to 85% RH at 85°C for 500 hours, the ChipCap sensor will need the same treatment as in #1, but perhaps for a longer period of time.
4. After being exposed to a high-temperature dry environment (dry packed storage or reflow soldering), the ChipCap sensor needs only to be rehydrated at 70% RH for 2-3 hours. Alternately, storage at 30 to 50% RH for one week will rehydrate the ChipCap humidity sensor.
Obviously the effectiveness will depend on how extreme and for how long the exposure time was to the conditions. However, the recommendations above will provide a good starting point in bring a sensor back its normal operational mode. In each case, the rate of recovery will depend on the environment, but these steps should help the sensor recover quickly.