Detection of blockage in a porous member

A gas sensor device to detect an analyte gas in an ambient environment, comprising:

• a housing comprising an inner chamber and a port;
• a porous member through which the analyte gas is transportable in operative connection with the port to separate the inner chamber from the ambient environment;
• a gas sensor responsive to the analyte gas positioned within the inner chamber;
• a source of pressure waves positioned within the inner chamber and spaced from the porous member so that pressure waves emitted from the source of pressure waves are propagated to the porous member and any pressure waves emitted from the source of pressure waves are emitted within the inner chamber, the source of pressure waves being configured to emit pressure waves at more than one frequency;
• a sensor responsive to pressure waves, different from the gas sensor responsive to the analyte;
• and
• circuitry in operative connection with the source of pressure waves and with the sensor responsive to pressure waves, the circuitry comprising a processor system and a memory system in operative connection with the processor system, the memory system comprising an algorithm stored therein which is executable by the processor system to drive the source of pressure waves in a predetermined manner and to relate a measured response of the sensor responsive to pressure waves reflected from the porous member at each of the more than one frequency to a state of blockage in the porous member, wherein a blockage of the porous member inhibits transport of analyte gas therethrough.