Reference

A poisoned catalytic bead sensor does not fault, blank or warn you. It reads low, silently, in a flammable atmosphere. This guide covers the compound classes that cause it, the difference between poisoning and inhibition, why calibration cannot fix it, and the daily function check that turns a silent failure into a visible one.

Cross-sensitivity is a sensor responding to a gas it was not built to measure, and it is not a defect but a property of the sensing chemistry itself. This guide covers the mechanism, the interference patterns crews actually meet, the under-reporting direction nobody expects, and how to diagnose a suspect alarm from clean air.