The Scintrex Model SC-595 Stack Sample Collector collects particulate and radioiodine constituent samples from air in the ventilation stack of a reactor building. An integral pump draws a sample of the ventilation stack air through isokinetic sampling nozzles. As the air sample travels through the system, two removable filter elements trap particulate and radioiodine constituent matter. The outlet of the pump returns the sample airstream to the stack. The system operator removes the filter element on a weekly basis and sends it to a laboratory for analysis.