What happens when a poison is ingested, injected, absorbed or inhaled. In gas detection, the term refers to rendering a sensor useless by inhibiting its detection principle, without causing a sensor fault. Most sensors can be poisoned by a too high concentration of its target substance. Catalytic Bead LEL sensors are susceptible to poisoning through a too high concentration of combustible gas (e.g. by holding an extinguished lighter to it) and silicons, which coat the catalyst beads, preventing the combusting reaction.