Astatic air sampling system can provide reasonable-to-high probability assurances of detecting an illicit gas-centrifuge uranium enrichment facility only in cases where either a very small grid constant or a very large source-term is assumed.There should be a higher probability of detecting a reprocessing facility,a gaseous-diffusion plant, or electromagnetic isotopic separation (EMIS) uranium enrichment sites.These probably would have larger source-terms, and some typical emissions of reprocessing plants, consisting of noble gases or volatiles, are harder to contain.In addition to being unwieldy, an air sampling array, with a gridconstant of some 50–100 kilometers, has a high probability of producing false-negative results.In the case of the proliferation of nuclear weapons, a false-negative report is impermissible.