Method and apparatus for integrating chemical and environmental sensors into an air purification filter

A sensor device 10 for end of service life indication, comprises a housing 14 having an outer surface, a longitudinal cavity, and at least one opening (16, Fig 2) along the outer surface. Also provided is a sensor (22a 22c) for detection of one or more chemicals, a sensor conditioning board (40, Fig 2) for processing sensor data from the sensor and a power supply for powering the sensor conditioning board. The housing is removably insertable into a cavity (50, Fig 3) in a sorbent bed (62, Fig 3) of a filter element. The sensor may be positioned within the longitudinal cavity adjacent the at least one opening. Data obtained from the one or more sensors can be used to calculate predicted end of service life of the filter element.