Evaluation of multichannel annular denuders for a newly develope ultrafine particle sampling system

Abstract

Laboratory studies evaluated the gas collection efficiencies and particle transmission efficiencies of 1-, 3-, 5-, and 8-channel denuders under simulated atmospheric conditions with the goal of combining an annular denuder-filter pack (AD-FP) system with a newly developed inertial classification. The multichannel denuders having large surface areas were considered for this AD-FP system since the inertial classification system operates at a flow rate of 40 L/min. Gas collection efficiency was measured with phosphorous acid-coated denuders targeted on ammonia gas. Particle transmission efficiency was measured for ammonium sulfate particles. The denuder-coating procedure and the method for extracting the multichannel denuders are described in detail. Gas collection efficiencies for the 1-, 3-, 5-, and 8-channel denuders were 96.3, 98.6, 98.2, and 98.3% (1-ch < 5-ch, 8-ch, and 3-ch), respectively. The extraction efficiency was greater than 96% for all but the 8-channel denuder (92%). The particle transmission efficiencies for the 1-, 3-, 5-, and 8-channel denuders at 40 L/min were 97.3, 97.4, 94.7, and 93.4% (8-ch < 5-ch < 1-ch and 3-ch), respectively. These results indicate that a 1- or 3-channel denuder can be effectively used in this AD-FP system at a flow rate of 40 L/min.