It is well documented that clothing serves as a reservoir of airborne particles, including bioaerosols. However, little is known about the role of clothing in transporting potentially harmful particles from one location to another that contribute to inhalation exposures. Here we utilize a well-controlled chamber to quantify the size-dependent clothing release fraction (CRF) in the particle diameter range 0.5-10 µm as a function of four fabric motion intensities and three motion types. A programmable robot reproducibly manipulated a fabric that had been previously loaded with a known quantity of test dust. Our results show that 0.3-3% of deposited particles were subsequently released with fabric motion. The percentage of resuspended particles increased with the vigor of fabric movement and varied with motion type. Particle size substantially influenced the CRF, with larger particles exhibiting higher values. These findings could contribute to understanding how bioaerosols are transmitted and controlled.

In this editorial, we have highlighted key research opportunities and challenges in four topical themes for indoor chemistry: human occupants as agents influencing indoor chemistry; oxidative chemistry; surface phenomena; and semivolatile organic compounds. In each case, enough prior work has been done to demonstrate the importance of the theme and to create a foundation for future studies. Extensive achievements and ongoing progress in (outdoor) atmospheric chemistry—both in the analytical methods developed and in the scientific knowledge created—also contribute to a strong foundation from which to achieve rapid research progress in this exciting new domain.

We present a model for the growth of organic films on impermeable indoor surfaces. The model couples transport through a gas-side boundary layer adjacent to the surface with equilibrium partitioning of semivolatile organic compounds (SVOCs) between the gas phase and the surface film. Model predictions indicate that film growth would primarily be influenced by the gas-phase concentration of SVOCs with octanol-air partitioning (K_oa ) values in the approximate range 10≤log K_oa ≤13. Within the relevant range, SVOCs with lower values will equilibrate with the surface film more rapidly. Over time, the film becomes relatively enriched in species with higher log K_oa values, while the proportion of gas-phase SVOCs not in equilibrium with the film decreases. Given stable airborne SVOC concentrations, films grow at faster rates initially and then subsequently diminish to an almost steady growth rate. Once an SVOC is equilibrated with the film, its mass per unit film volume remains constant, while its mass per unit area increases in proportion to overall film thickness. The predictions of the conceptual model and its mathematical embodiment are generally consistent with results reported in the peer-reviewed literature.

Strong evidence suggests that clothing serves as a reservoir of chemical pollutants and particles, including bioaerosols, which may have health significance. However, little is known about the role that clothing may play as a transport vector for inhaled airborne particles. Here, we contribute toward bridging the knowledge gap by conducting experiments to investigate clothing release fraction (CRF), determined as the size-dependent ratio of released to deposited particulate matter in the diameter range 0.5-10 μm. In a fully controlled chamber with low background particle levels, we deployed a programmable robot to reproducibly quantify the size-dependent CRF as a function of motion type and intensity, dust loadings, and activity duration. On average, 0.3%-3% of deposited particles were subsequently released with fabric motion, confirming that clothing can act as a vehicle for transporting airborne particles. The CRF increased with the vigor of movement and with dust loading. Rubbing and shaking the fabric were more effective than fabric stretching in resuspending particles. We also found that most of the release happened quickly after the onset of the resuspension activity. Particle size substantially influenced the CRF, with larger particles exhibiting higher values.

Absent unvented combustion, in occupied indoor spaces, CO2 concentrations depend primarily on three factors: Outdoor CO2 concentrations, CO2 emission rates from human metabolism, and the outdoor-air ventilation rate. Indoor CO2 levels are generally managed by means of dilution with outdoor air. In this work, we investigate an alternative approach to controlling indoor CO2: Active removal using a solid sorbent. We report parameterizations of chemical kinetics and uptake capacity to soda-lime sorbent across a range of conditions relevant to indoor environments. Reaction rate constants for the interaction of Ca(OH) 2 present in soda-lime and CO2 range from 1.8×10-2 to 1.5×10-1 m2 mol-1 s-1, increasing with higher relative humidity (RH). Uptake capacities range from 0.04 to 0.36 g CO2/g sorbent, also increasing with higher RH. These data facilitate assessment of the technical feasibility of soda-lime scrubbers in buildings as an option for controlling indoor CO2.

Using an ultraviolet-light induced fluorescence (UV-LIF) technique, we measured number concentrations of total aerosol particulate matter (tPM) and fluorescent biological aerosol particles (bioPM) (1.0-3.0 µm and 3.0-5.0 µm diameter) in an office and outdoors, sampling with 1-min resolution. The air-conditioning and mechanical ventilation (ACMV) system equipped with high-grade filters was effective in controlling both tPM and bioPM indoors. As expected, removal efficiencies were found to be size dependent. One human subject walking on the carpet was found to be a strong contributor to bioPM, resulting in 2-3 times higher concentration than that outdoors. Compared to the times when the room is vacant, the biological proportion of total airborne particles increased by an order of magnitude during the light walking period. Consequently, indoor-to-outdoor ratios depend on the ACMV operating conditions and on human activities. This pilot study provides preliminary data concerning the bioPM levels in an indoor environment equipped with an ACMV system. Ongoing investigations using this approach promise to improve our understanding of the processes that influence indoor bioaerosol levels and the effectiveness of control alternatives.