Breathing simulator of workers for respirator performance test

Jung

et al. 2021

ACS Appl. Nano Mater.

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.

Section: Simulated Intermittent Exposure Conditionsmentioning

confidence: 99%

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

Jung

et al. 2021

ACS Appl. Nano Mater.

“…Some researchers used cough simulators to evaluate the effectiveness of air ventilation systems in confined spaces [ 140 ]. Others investigated the influence of thermal buoyancy (resulting from human body temperature) on particle movements using a breathing simulator and thermal manikin [ 141 , 142 , 143 ]. National agencies including the US National Personal Protective Technology Laboratory (NPPTL) have used head manikins to assess respirator fit [ 144 , 145 , 146 ].…”

Section: Rpd Performance Issues and Challengesmentioning

confidence: 99%

What We Are Learning from COVID-19 for Respiratory Protection: Contemporary and Emerging Issues

Zhang

et al. 2021

Polymers

Infectious respiratory diseases such as the current COVID-19 have caused public health crises and interfered with social activity. Given the complexity of these novel infectious diseases, their dynamic nature, along with rapid changes in social and occupational environments, technology, and means of interpersonal interaction, respiratory protective devices (RPDs) play a crucial role in controlling infection, particularly for viruses like SARS-CoV-2 that have a high transmission rate, strong viability, multiple infection routes and mechanisms, and emerging new variants that could reduce the efficacy of existing vaccines. Evidence of asymptomatic and pre-symptomatic transmissions further highlights the importance of a universal adoption of RPDs. RPDs have substantially improved over the past 100 years due to advances in technology, materials, and medical knowledge. However, several issues still need to be addressed such as engineering performance, comfort, testing standards, compliance monitoring, and regulations, especially considering the recent emergence of pathogens with novel transmission characteristics. In this review, we summarize existing knowledge and understanding on respiratory infectious diseases and their protection, discuss the emerging issues that influence the resulting protective and comfort performance of the RPDs, and provide insights in the identified knowledge gaps and future directions with diverse perspectives.

“…Another consideration is that, as face velocity increases, the ability of aerosol particles to penetrate through the material increases (Stevens and Moyer, 1989;Eninger et al, 2008b) and the MPPS decreases (Eninger et al, 2008a;Huang et al, 2013). Face velocities that occur during inhalation and exhalation differ between individuals, and for the same individual during different activities (Anderson et al, 2006;Yuasa et al, 2015). Velocities consistent with breathing during moderate or strenuous activity may result in the decrease of MPPS to < 100 nm (Eninger et al, 2008a).…”

Section: Accepted Manuscriptmentioning

confidence: 99%

What to Wear: The Filtration Performance of Alternative Materials Used to Construct Do-It-Yourself Masks

Mirrielees

Chen

Moreno

et al. 2021

Aerosol Air Qual. Res.

The COVID-19 pandemic has shown that much of the world, including the United States, is illprepared for the material demands of a global crisis. In response to this shortage of Personal Protective Equipment (PPE), we have conducted filtration efficiency and pressure drop testing of a range of common materials used for constructing do-it-yourself masks, including an allergen filter, a vacuum bag, a heavy-duty tool wipe, and a standard cotton bandana, as well as a standard 3-ply surgical mask, a medical drape and an industrially available composite filter material. Size-resolved percent penetration of each material by particles with diameters ranging from 25 to 500 nm was measured at three face velocities (0.72 cm s -1 , 4.30 cm s -1 , 13.0 cm s -1 ). The allergen filter performed best, only allowing the penetration of 5% ± 3% of the 300 nm particles through the material at a face velocity of 13.0 cm s -1 , comparable to human breathing during heavy physical work. In comparison, the surgical mask and the cotton bandana allowed 39 ± 1% and 51% ± 1% of the 300 nm particles to pass through at the same face velocity, respectively. According to the calculated filter quality, the best choices for mask construction are the allergen filter, industrial composite filter, and the vacuum bag. Structure and morphology of the materials were characterized by scanning electron microscopy (SEM), image analysis, and thickness measurements to investigate physical characteristics which improve filtration. This study shows that certain household and commercially available materials and combinations can be used in the construction of highly effective face masks.