Particle Losses in Glass Honeycomb Denuder Samplers

Abstract

Particle loss tests have been performed on glass honeycomb denuders for particles in the size range 0.05–2 (Am. The tests were conducted at three different flow rates (1.5, 4, and 10 L/min). Fluorescent monodisperse latex particles were used as a test aerosol. Experimental results were compared to those predicted by the theory that combines diffusion, impaction, and interception. It was demonstrated that particle losses reach a minimum for particles in the range 0.5–0.75 (μm and become higher for smaller or larger particles. Although for every flow rate tested the particle losses appear to be higher than the predictions of theory, they exhibit similar trends with the theoretical predictions. In all cases the particle losses on the glass honeycomb denuder were found to be < 5%. The effect of relative humidity on particle loss was examined at 1.5 L/min sampling flow rate. The results did not demonstrate a dependence of the loss on the humidity. It was expected that a lower relative humidity (10% to 20%) would accentuate losses due to electrostatic charges. Particle loss tests were conducted for uncoated denuders as well as denuders coated with citric acid. Although in both cases the losses are small, they appear to be smaller on coated denuders, as expected. Finally, collocated fine particle mass sampling was conducted using the Harvard-Marple impactor and an impactor/denuder sampler using two glass honeycombs. The mass collected on the honeycomb denuder sampler was approximately 5% lower than on the Harvard-Marple impactor.