A trigger device for detecting particles of interest comprises a sample substrate, a collector, a read head and a processor. The collector is positioned proximate to at least a portion of a first side of a sample substrate and is operated to deposit a sample on the substrate within a sample area. The read head is positioned proximate to the sample area on a second side of the sample substrate generally opposite the collector and comprises a concave reflection surface having a back side positioned proximate to the sample area so as to register the substrate within the sample area with the read head. The processor is operatively configured to analyze a signal from one or more detectors of the read head and to trigger an event if particulates of interest are detected in the sample.