SINCE ALMOST ALL HUMAN ACTIVITY RESULTS IN SOME EFFLUENT WHICH BECOMES AIRBORNE FROM THE SCENE OF ACTIVITY, INSTRUMENTS WHICH CAN DETECT TRACE ELEMENTS IN THE ATMOSPHERE HAVE WIDE APPLICATION IN ENVIRONMENTAL SAFETY INSPECTIONS, LAW ENFORCEMENT, AND MILITARY SITUATIONS. A NATIONAL SCIENCE FOUNDATION-U.S. ARMY PROJECT WORKED ON CALIBRATION FOR SUCH DETECTORS; THE RESULT WAS A TWO-STAGE DILUTION SYSTEM WHICH GIVES ACCURATE READINGS AT LOW LEVELS OF CONCENTRATION. THIS SYSTEM IS APPLICABLE TO MASS SPECTROMETER AND/OR ELECTRON CAPTURE AND FLAME IONIZATION DETECTORS. ITS OPERATION IS DESCRIBED IN DETAIL. DESCRIPTIONS ARE ALSO GIVEN FOR CONDENSATION NUCLEI DETECTORS, ELECTRON CAPTURE DETECTORS, THE ION MOBILITY SPECTROMETER, THE ELECTRIC QUADRUPOLE MASS SPECTROMETER, THIN FILM DETECTORS, AND BIOCHEMICAL DETECTORS USING BIOLUMINESCENT STRAINS OF BACTERIA. USE OF ANIMALS AS DETECTORS REMOTE AND REMOTE SENSORS ARE ALSO DISCUSSED. TABLES PROVIDE RESPONSE CHARACTERISTICS OF THE VARIOUS DETECTORS. TYPICAL SPECTRUMS ARE ILLUSTRATED AND DIAGRAMS DETAIL METHODS OF OPERATION. THE TECHNICAL REPORTS CITED IN THE REPORT ARE INCLUDED IN FOOTNOTES. A BIBLIOGRAPHY IS APPENDED. SUCH SENSORS ARE CONSIDERED IMPORTANT FOR DETECTING EXPLOSIVES AND NARCOTICS, AND FOR LOCATING THE SITE OF MANUFACTURE OF ILLEGAL DRUG COMPOUNDS. IT IS PREDICTED THAT THE USEFULNESS AND SOPHISTICATION OF SUCH INSTRUMENTS WILL INCREASE AS THEIR NONMILITARY APPLICATIONS ARE APPRECIATED. (GLR)