We disclose a circuit board that hosts at least first and second types of resistance sensors. The resistance of each sensor of the first type tends to increase, and the resistance of each sensor of the second type tends to decrease if the sensor is exposed to an aggressive environment. The circuit board also hosts a control circuit that operates to monitor respective resistances of the various resistance sensors and to process the digital values representing the resistances to estimate the working condition of one or more other electrical circuits located on the circuit board and/or in relatively close proximity to the circuit board in the corresponding equipment cabinet. The control circuit further operates to transmit out an appropriate alarm message if the estimated working condition is deemed unsatisfactory.