What is indicated by a blue humidity indicator on a PBE unit?

A blue humidity indicator on a Protective Breathing Equipment (PBE) unit signifies that the unit is sealed and usable. The primary function of this indicator is to provide visible confirmation of the unit's integrity and readiness for use. When the indicator is blue, it indicates that the internal environment of the PBE is within the acceptable humidity range, confirming that no moisture has compromised the contents.

This is crucial for safety; if the humidity indicator were to change color, it would suggest that the unit might have been exposed to conditions that could affect its usability or safety. Therefore, a blue indicator assures users that the PBE is in optimal condition for deployment in emergency situations.