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

Figures & data

Figure 1. Diagram of the human exposure chamber: (a) Teflon bag; (b) human exposure chamber; (c) internal air circulation pump; (d) bag-chamber transfer pump; (e) bag-to-chamber transfer line; (f) bag purge line; (g) clean air filling line; (h) combustion emissions intake line and catalyst; (i) chamber-to-bag transfer line; (j) bag sampling manifold, UV lights not shown; (k) particle control transfer values; and (l) chamber sampling manifold. The sampling manifolds are also used in conjunction with item e.

Figure 2. Oven setup for burning wood or coal: (a) oven, (b) Bunsen burner (used only for coal ignition), (c) air supply tube, (d) stainless steel mesh, (e) PM intake tube, (f) catalyst enclosure, and (g) fuel (coal or wood).

Figure 3. Normalized decay of wood smoke and photochemically aged wood and coal smoke as measured with a TEOM in the Teflon bag. The decay curve for non-aged coal smoke was indistinguishable from that of aged coal smoke and for that reason is not included in this figure. The apparent curvature and elevation of the photo-chemically aged wood smoke over the regular wood and coal smoke decay plots suggest secondary particle formation. The decay rates display particle decay in the unperturbed bag environment and do not represent the decays observed during the actual experiments.

Figure 4. (a) SEM image of coal smoke particles collected on a Nucleopore membrane filter (pore size 0.4 μm). (b) SEM image of photochemically aged wood smoke particles collected on a Nucleopore membrane filter. Both sets of particles are <2.5 μm in size but have different textures.

Table 1. Results of ion chromatographic anion analysis of aged wood and coal combustion particles collected from the Teflon bag with 0.4 μm PTFE filters

	Aged Wood Smoke	Coal Smoke
Cl^−	0.00 ± 0.01%	0.42 ± 0.01%
NO2−	0.03 ± 0.00%	0.24 ± 0.01%
NO3−	7.01 ± 0.9%	0.52 ± 0.01%
PO4 ^3−	0.00 ± 0.01%	0.92 ± 0.4%
SO4 ^2−	1.16 ± 0.01%	1.70 ± 0.01%
EC	23 ± 12%	31 ± 12%
OM	68 ± 12%	58 ± 12%
Notes: Concentrations are given as the mass percentage of the total weight of the collected PM. Uncertainty is given as absolute error in the percentage. Two filter samples were analyzed.

Table 2. X-Ray fluorescence elemental analysis data for aged wood and coal combustion particles

	Aged Wood Smoke	Coal Smoke
K	8.39 ± 0.04%	0.24 ± 0.03%
S	1.36 ± 0.11%	2.01 ± 0.15%
Cl	0.27 ± 0.03%	0.42 ± 0.04%
Zn	0.34 ± 0.02%	0.35 ± 0.02%
Fe	0.00 ± 0.04%	0.14 ± 0.06%
Ca	0.25 ± 0.03%	0.00 ± 0.04%
Pb	0.00 ± 0.04%	0.06 ± 0.06%
Hg	0.00 ± 0.013%	0.00 ± 0.015%
Notes: Concentration of elements expressed in wt/wt % ratio. Two sample filters were analyzed.

Figure 5. EC, OC, and EC/TC from coal smoke as a function of time with UV photochemical aging.

Figure 6. Gas and PM concentrations using photochemically aged wood smoke during a typical human exposure experiment. The average values of concentrations of gases and PM were held under regulatory standards and within experimental protocols.