A Simple and Disposable Sampler for Inhalable Aerosol

Abstract

The state-of-the-art for personal sampling for inhalable aerosol hazards is constrained by issues of sampler cost and complexity; these issues have limited the adoption and use of some samplers by practicing hygienists. Thus, despite the known health effects of inhalable aerosol hazards, personal exposures are routinely assessed for only a small fraction of the at-risk workforce. To address the limitations of current technologies for inhalable aerosol sampling, a disposable inhalable aerosol sampler was developed and evaluated in the laboratory. The new sampler is designed to be less expensive and simpler to use than existing technologies. The sampler incorporates a lightweight internal capsule fused to the sampling filter. This capsule-filter assembly allows for the inclusion of particles deposited on the internal walls and inlet, thus minimizing the need to wash or wipe the interior sampling cassette when conducting gravimetric analyses. Sampling efficiency and wall losses were tested in a low-velocity wind tunnel with particles ranging from 9.5 to 89.5 μm. The results were compared to the proposed low-velocity inhalability criterion as well as published data on the IOM sampler. Filter weight stability and time-to-equilibrium were evaluated as these factors affect the practicality of a design. Preliminary testing of the new sampler showed good agreement with both the IOM and the proposed low-velocity inhalability curve. The capsule and filter assemblies reached equilibrium within 25h of manufacturing when conditioned at elevated temperatures. After reaching equilibrium, the capsule-filter assemblies were stable within 0.01mg.

Keywords: air pollution; exposure; low cost; particulate matter; sampling efficiency; wall deposits.

Figure 1

Left: Disassembled IOM sampler. Right: Exploded view of the new sampling system (a) inlet cover, (b) inlet, (c) capsule and filter, and (d) housing.

Figure 2

Low-velocity wind tunnel used for testing the new sampler design. The tunnel was operated at 0.1 and 0.2 m s⁻¹ (particle size dependent), with particles distributed using a TOPAS Solid Aerosol Generator 410 (TOPAS, Dresden, Germany). (a) Particles between 9.5 and 60.1 µm were distributed through a dispersion tube that transverse the width of the tunnel and oscillated through a 45° arc. Larger particles were dispersed from the top of the wind tunnel. (b) Samplers were attached to the lapel of a manikin that rotated clockwise 360° and then 360° counterclockwise. The manikin was 4 m from the flow conditioner. The tunnel includes (c) pre-filters, (d) high efficiency particulate air filters, (e) a flow conditioner, and (f) post-filters.

Figure 3

Sampling efficiency of capsules compared to previous IOM studies and the modified inhalability criterion. Error bars represent pooled variance of all samplers and replicate tests at each particle size evaluated.

Figure 4

Size distribution of particles collected on the (a) filter and (b) interior capsule walls. The plots represent the size distribution of particles collected on the walls and filter. The y-axis is the log-transformed fraction of particles in each histogram bin.

Figure 5

Mass change of test capsule and filter assemblies after the chemical bonding process in days when stored at 20°C and when stored at 70°C.