Design and Characterization of a Two-Stage Human Subject Exposure Chamber

摘要

A human subject exposure chamber, designed to hold six to eight subjects, coupled to an approximately 30-m3 Teflon reaction bag was designed and built to provide exposures that mimic the production and photochemical oxidation of atmospheric pollutants resulting from the combustion of coal or wood from a stove. The combustion products are introduced into the Teflon bag under atmospheric conditions. Photochemical oxidation of this mixture is accomplished by exposure to tropospheric sun-like radiation from an array of ultraviolet and black lamps. The aerosol in the Teflon reaction bag is then transferred into the exposure room to maintain a constant, lower exposure level. Continuous and semicontinu-ous monitoring of the gas and particulate matter (PM) pollution in the exposure room and the reaction bag is accomplished using a suite of instruments. This suite of instruments allows for the measurement of the concentrations of total and nonvolatile PM, nitric oxide, nitrogen dioxide, carbon monoxide, carbon dioxide, and ozone. The concentration of the particles was monitored by an R&P tapered element oscillating microbalance monitor. The chemical composition of the PM and its morphological characterization is accomplished by collecting samples in filter packs and conducting ion chromatography, elemental X-ray fluorescence, and scanning electron microscopy analyses. The concentration and composition of emissions from combustion of wood and coal is described. The results of this study suggest that although the bulk compositions of particulate emissions from the combustion of coal or wood in a stove have many similarities, the wood smoke aerosol is photochemically reactive, whereas the coal smoke aerosol is not.