Probing the Nanoparticle Loading Characteristics and the Filtration Performance with the Continuous and Intermittent Use of Disposable Filtering Masks

Abstract

With the pandemic crisis and long-lasting air pollution, reuse of disposable filtering masks has been prevalent while not being recommended. Different aerosol exposure conditions such as an extended continuous use and an intermittent repeated use lead to different particle loading behavior, affecting the effective service life of filters in terms of resistance and efficiency. Thus, the service life analysis considering the realistic wear situation is needed for guiding the proper filtering mask usage. This work investigated the effect of particle exposure and storage conditions on the performance and resistance of a single use, disposable foldable type filtering masks. An intermittent exposure condition was set to simulate a harsh exposure scenario of particle concentration of 300 μg/m 3 , 8−10 h use, and intense physical load with 85 L/min inhalation rate. For an extended use situation with solid particles, resistance was a limiting factor of the effective useful time of filtering mask. Compared with the continuous exposure, the intermittent exposure with humid storage condition accelerated the performance deterioration, limiting the service life. The causes for the divergent performance behavior were probed in the nanoscale, employing the Xμ-CT analytical technique; this allowed visualization of distinctive loading characteristics of aerosol, such as surface clogging, depth filtration, and aerosol aggregation. The significance of this study lies in the analytical approach that enabled the 3D probing of nanoparticle-loaded filters and in the experimental design that mimicked the practical use conditions.

Tetrazolium-Based Visually Indicating Bacteria Sensor for Colorimetric Detection of Point of Contamination

“…2 Particularly, timely alert for biological contamination of sanitary materials is critical as it can serve as a secondary source of infection, 3 leaving aside the performance deterioration by the exposure to bioaerosols. 4 The conventional method of bacteria quantification employs spectrophotometric assay 5−7 or plate counting 8 via extracting bacteria from the contaminated surfaces. Although these procedures are considered reliable, they require laborious steps.…”

Sequential Multiscale Simulation of a Filtering Facepiece for Prediction of Filtration Efficiency and Resistance in Varied Particulate Scenarios

“…In the particulate environment with solid particles (not liquid aerosol), the efficiency tends to become higher with time, as the filter pores become blocked. 9 Thus, high breathing resistance is a common restrictor that limits the usage life of a facepiece in such an environment. According to previous studies, filtering respirator users recognized a noticeable breathing resistance when the resistance of the filter increased by about 15−20% from the initial resistance.…”

“…The effective service life of a facepiece can be determined by the breathing resistance and/or the filtration efficiency. In the particulate environment with solid particles (not liquid aerosol), the efficiency tends to become higher with time, as the filter pores become blocked . Thus, high breathing resistance is a common restrictor that limits the usage life of a facepiece in such an environment.…”

“…The effective service life of a filtering facepiece is affected by the deteriorated filtration efficiency and the resistance buildup that limits the breathing flow. , Previous research reported that filtering respirator users discarded the used filters when they sensed breathing inconvenience at 15–20% higher resistance than the initial one. − The buildup of resistance is influenced by environmental factors such as particle size and concentration and user factors such as breathing rate (or flow rate) and wearing time. Therefore, the filtration behavior and service life for different scenarios cannot be accurately predicted by the regulatory test method.…”

“…In another study, a work environment was simulated by generating wood dust and plastic aerosol in a laboratory-scale setup . Experimenting with practical environmental scenarios, those studies reported that filter performance was highly affected by the particle type and size distribution. ,, Altogether, while the varied environments and use conditions affect the filtration efficiency and resistance during the particulate mass loading, setting diverse test conditions with varied parameters is costly and not practical. Also, it is not always possible to conduct a field test.…”