A distributed biohazard surveillance system including a plurality of robust miniaturized remote monitoring stations for the detection, localized analysis and reporting of a broad range of biohazards. In a first aspect, a pump is provided having an actuator with a nozzle and a releasable cap having a first shield located to entrap a fixed volume of air about the nozzle. Horizontally adjacent cladding panels of the matrix of unitized cladding panels are responsively joined to a cable type structural member via an anchor fixture, which allows the structural member to move freely along the wall. If the variance sum is greater than the threshold, it is determined that a detected step is a walking step. The measuring apparatus can measure a micro difference or variation of the electric conductivity between a plurality of measuring points different in position or time with high reliability, accuracy and sensitivity. These probes and methods are useful for the detecting whether test samples, including food and water samples, are infected with enteric bacteria.