Patent ID: 8537020

Claim:
A gas detector comprising: a housing with at least one gas inflow port; an electro-chemical gas sensor carried in the housing, adjacent to the gas inflow port, the gas sensor responding to a first gas; and a plurality of colorimetric materials visible, at least in part, from outside of the housing, the colorimetric materials responding to at least a second, different gas, where the colorimetric materials detect and indicate the presence of chemicals or compounds that impair the performance or function of the electro-chemical gas sensor in a region monitored by the electro-chemical gas sensor, the colorimetric materials are printed on the housing or on a member carried by the housing; and a gas permeable member carried by the housing in a vicinity of the at least one gas inflow port, wherein a central region of the gas permeable membrane passes the first gas to the electro-chemical gas sensor, and wherein an outer annular region of the gas permeable membrane carries at least one of the plurality of colorimetric materials.