New measurements of resonance ionization detection limits are presented for seven species, of high thermal stability, which are potentially useful surrogates for continuous emission monitoring of incinerator effluent. Resonance ionization detection limit data are now available for 20 aliphatic and aromatic compounds; eight of these compounds have sub part-per-billion detection limits. These eight also exhibit selectivities exceeding 103when detected in the presence of a “soup” of chemically similar interferant species likely to be present in stack gas samples. Preliminary measurements indicate that detection limits, obtained under ideal conditions in a helium carrier gas, are also approached under adverse sampling conditions tested with synthetic “soups”. The implications of these measurements on the selection of surrogates and the prospects for repetitive on-line hazardous emissions monitoring are discussed