Masks and filters are worn over the head or face in order to protect individuals from exposure to toxic chemical vapors. In these devices, there is no convenient or effective way to tell whether the adsorbent in the mask is fresh or used. A sensor that could fit inside the protective sorbent bed and tell the remaining useful lifetime of the filter would be ideal. In this work, a micropower microsensor is designed and fabricated. This sensor can fit inside a carbon adsorbent bed and tell whether the filter is operating properly or whether it is used and hazardous vapors are penetrating the protective device. The sensor is designed into a cannister filter and the feasibility of an advanced respiratory protective device that can alert the user when it is no longer effective is assessed.