Quick laboratory methodology for determining the particle filtration efficiency of face masks/respirators in the wake of COVID-19 pandemic

2020 ◽  
pp. 152808372097508
Author(s):  
Manish Joshi ◽  
Arshad Khan ◽  
BK Sapra
Keyword(s):  
Pressure Drop ◽  
Filter Material ◽  
Filtration Efficiency ◽  
Capture Efficiency ◽  
Particle Capture ◽  
Particle Filtration ◽  
Mask Design ◽  
Mask Material ◽  
Present Context ◽  
The Times

Recent crisis in the form of COVID-19 has rendered wearing of mask mandatory for patients, health care workers and members of public worldwide. This has caused a sudden shift of focus on availability, effectiveness, re-use and development of face masks/respirators. In the current pandemic situation, the shortage of masks has also led to rethinking on strategies of reuse of masks after due sterilization. This work discusses a quick laboratory methodology to test/determine the particle filtration efficiency of face masks/respirators. The testing parameters include the particle capture efficiency of the mask material/full mask, pressure drop and the fit factor. Two different, simple, make-shift set-ups have been adopted for the present context. The first is used to measure the intrinsic particle capture efficiency and pressure drop of the filter material and the second as a ‘full mask sampler’ to assess the leakages through seams and joints of the mask. Experiments conducted with atomized NaCl test particles on three types of mask viz. commercial N-95 respirator, surgical mask and cloth mask have been used for evolving the methodology. The differences in terms of capture efficiency of aerosol particles for the filter material and for the full mask in face fix/sealed fixture have been linked to improvement of the mask design in development phase. This paper hopes to provide a crucial laboratory link between the mask developers and the certification agencies in the times of urgency. Needless to mention that commercialization of the same is subject to certification from authorized agencies, following standard procedures.

scholarly journals Quick laboratory methodology for determining the effectiveness of face mask respirators in the wake of COVID-19 pandemic

2020 ◽  
Author(s):  
Manish Joshi ◽  
Arshad Khan ◽  
B. K. Sapra
Keyword(s):  
Pressure Drop ◽  
Particle Diameter ◽  
Filter Material ◽  
Face Mask ◽  
Capture Efficiency ◽  
Particle Capture ◽  
Mask Material ◽  
Present Context ◽  
The Face ◽  
The Times

Abstract Recent crisis in the form of COVID-19 has rendered wearing a face mask mandatory for patients, health care workers and even members of public worldwide. This has caused a sudden shift of focus on availability, effectiveness, re-use and development of face masks. It is imperative that commercialization of face masks is subjected to certification, following standard procedures, from authorized agencies. However, at times, there is a need to conduct a quick investigation on their performance, specially, when new materials are being used for making the masks. In the current pandemic situation, the shortage of masks has also led to a rethinking on strategies of reuse of masks after due sterilization. For such situations, a quick laboratory methodology to test/determine the effectiveness of face mask respirators has been developed. The testing parameters include the particle capture efficiency of the mask material, pressure drop and the fit factor. Two different, simple, make-shift set-ups have been adopted for the present context. The first is used to measure the intrinsic particle capture efficiency and pressure drop of the filter material and the second is employed as a ‘full mask sampler’ to assess the leakages through seams and joints. For particle filtration efficiency, measurements in optical particle diameter range (0.3-20 µm) are most important as they cover the most penetrating particle size (MPPS) range; nevertheless, we also measured aerosol number concentration in sub-micrometer and ultrafine size ranges. Experiments conducted with atomized NaCl test aerosols, using these setups on three types of face masks viz. commercial N-95, surgical mask and cloth mask have been used for the validation and interpretation of results. This paper hopes to provide a crucial laboratory link between the face mask developers and the final certification agencies in the times of urgency.

Microwave structured polyamide-6 nanofiber/net membrane with embedded poly(m-phenylene isophthalamide) staple fibers for effective ultrafine particle filtration

2016 ◽  
Vol 4 (16) ◽  
pp. 6149-6157 ◽  
Author(s):  
Shichao Zhang ◽  
Hui Liu ◽  
Jianyong Yu ◽  
Wenjing Luo ◽  
Bin Ding
Keyword(s):  
Pressure Drop ◽  
Ultrafine Particle ◽  
Polyamide 6 ◽  
Low Pressure ◽  
Filtration Efficiency ◽  
Airborne Particles ◽  
Particle Filtration

Microwave structured PA-6/PMIA NFN membrane can filter airborne particles with high filtration efficiency, low pressure drop, and large dust-holding capacity.

scholarly journals Assessment of Fabric Masks as Alternatives to Standard Surgical Masks in Terms of Particle Filtration Efficiency

2020 ◽  
Author(s):  
Amy Mueller ◽  
Loretta Fernandez
Keyword(s):  
Health Care Providers ◽  
Ambient Air ◽  
Filtration Efficiency ◽  
Airborne Particles ◽  
Particle Removal ◽  
Breathing Zone ◽  
Care Providers ◽  
Particle Filtration ◽  
Surgical Masks ◽  
Mask Design

AbstractIn response to the critical shortage of medical masks resulting from the COVID-19 pandemic, large portions of the population are mobilizing to produce cloth masks using locally-sourced fabrics, however the efficacy of these masks as a means of protecting the wearer from airborne particles carrying virus is not well known. Further, existing protocols are designed for testing the fit and performance N95 respirators and tight-fitting facemasks rather than the relatively more loose-fitting surgical mask style most cloth masks follow. In this study tools and methods typically used to assess tight-fitting facemasks were modified to assess the efficacy of community-produced fabric and commercially-produced surgical masks in terms of protecting the wearer from airborne particles that may be carrying virus. Two TSI PortaCount (model 8028) instruments were operated concurrently to collect particle counts (particles/cm3) in size range 0.02 to >1 µm from ambient air and air just inside the breathing zone of the mask (1 measurement per second, evaluation period of 1 minute per test). Percent particle removal was determined for ten home-made, fabric masks of different designs, with and without filter layers, as well as three commercially-produced surgical-type masks. N95 masks were used to validate the method, and a 3M model 1826 surgical mask was used as a baseline for comparison of other masks of this style. Home-made masks worn as designed always had lower particle removal rates than the 3M masks, achieving between 38% and 96% of this baseline. As has been previously observed by Cooper et al. (1983), adding a layer of nylon stocking over the masks minimized the flow of air around the edges of the masks and improved particle filtration efficiency for all masks, including all commercial products tested. Use of a nylon stocking overlayer brought the particle filtration efficiency for five of the ten fabric masks above the 3M surgical mask baseline. This rapid testing method (<2 hours per mask design) provides a holistic evaluation of mask particle removal efficacy (material, design, and fit), and use of this method for testing a wider range of mask materials and designs will provide the public and health care providers with information needed to optimize health protection given resources at hand.

scholarly journals High-Quality and Easy-to-Regenerate Personal Filter

2021 ◽  
Author(s):  
Max Fraenkl ◽  
Milos Krbal ◽  
Jakub Houdek ◽  
Zuzana Olmrova Zmrhalova ◽  
Borivoj Prokes ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Volumetric Flow Rate ◽  
Filter Material ◽  
Polyester Fabric ◽  
Filtration Efficiency ◽  
High Quality ◽  
Novel Approach ◽  
Key Factor ◽  
Green Solution ◽  
Filter Cartridge

Proper respiratory tract protection is the key factor to limiting the rate of COVID-19 spread and providing a safe environment for health care workers. Traditional N95 (FFP2) respirators are not easy to regenerate and thus create certain financial and ecological burdens; moreover, their quality may vary significantly. A solution that would overcome these disadvantages is desirable. In this study a commercially available knit polyester fleece fabric was selected as the filter material, and a total of 25 filters of different areas and thicknesses were prepared. Then, the size-resolved filtration efficiency (40-400 nm) and pressure drop were evaluated at a volumetric flow rate of 95 L/min. We showed the excellent synergistic effect of expanding the filtration area and increasing the number of filtering layers on the filtration efficiency; a filter cartridge with 8 layers of knit polyester fabric with a surface area of 900 cm2 and sized 25 x 14 x 8 cm achieved filtration efficiencies of 98 % at 95 L/min and 99.5 % at 30 L/min. The assembled filter kit consists of a filter cartridge (14 Pa) carried in a small backpack connected to a half mask with a total pressure drop of 84 Pa at 95 L/min. In addition, it is reusable, and the filter material can be regenerated at least ten times by simple methods, such as boiling. We have demonstrated a novel approach for creating high-quality and easy-to-breathe-through respiratory protective equipment that reduces operating costs and is a green solution because it is easy to regenerate.

scholarly journals Durability of Disposable N95 Mask Material When Exposed to Improvised Ozone Gas Disinfection

2020 ◽  
Vol 2 (1) ◽  
Author(s):  
Robert Dennis ◽  
Behnam Pourdeyhimi ◽  
Avery Cashion ◽  
Steve Emanuel ◽  
Devin Hubbard
Keyword(s):  
Mechanical Damage ◽  
Filter Material ◽  
Electrostatic Charge ◽  
Filtration Efficiency ◽  
Significant Loss ◽  
Extensive Literature ◽  
Viral Inactivation ◽  
Mask Material ◽  
Filtration Material ◽  
Ozone Disinfection

The principle finding of this report is that both commercial and a novel material used for N95 mask filters can endure many cycles of disinfection by ozone gas (20 ppm for 30 minutes) without detectable degradation or loss of filtration efficiency.  N95 masks and surgical masks (hereafter referred to as masks) typically use a filtration material fabricated from meltblown polypropylene.  To achieve maximum filtration efficiency while maintaining a reasonable pressure drop, these nonwoven fabrics are also electrostatically charged (corona discharge is the most common method used), to maximize attraction and capture of aerosols and solid particulates.  Under normal circumstances, the reuse of masks is generally discouraged, but in times of crisis has become a necessity, making disinfection after each use a necessity.  To be acceptable, any disinfection procedure must cause minimal degradation to the performance of the filter material.  Possible performance degradation mechanisms include mechanical damage, loss of electrostatic charge, or both.  One of the most practical and direct ways to measure combined mechanical and electrostatic integrity, and the subsequent ability to reuse mask filter material, is by the direct measurement of filtration efficiency. In this paper, we report that small numbers of disinfection cycles at reasonable virucidal doses of ozone do not significantly degrade the filtration efficiency of meltblown polypropylene filter material. By comparison, laundering quickly results in a significant loss of filtration efficiency and requires subsequent recharging to restore the electrostatic charge and filtration efficiency. A common assumption among biomedical scientists that ozone is far too destructive for this application.  However, these direct measurements show that mask materials, specifically the filtration material, can withstand dozens of ozone disinfection cycles without any measurable degradation of filtration efficiency, nor any visible discoloration or loss of fiber integrity.  The data are clear: when subjected to a virucidal dose of ozone for a much longer duration than is required for viral inactivation, there was no degradation of N95 filtration efficiency.  The specific dosages of ozone needed for ~99% viral inactivation are thought to be at least 10 ppm for up to 30 minutes based upon an extensive literature review, but to standardize our testing, we consider a dose of 20 ppm for 30 minutes to be a reasonable and conservatively high ozone disinfection cycle.  The material tested in this study withstood dosages of up to 200 ppm for 90 minutes, or alternatively 20 ppm for up to 36 hours, without detectable degradation, and further testing suggests that up to 30 or more disinfection cycles (at 20 ppm for 30 minutes) would result in less than a 5% loss of filtration efficiency. This report does not address the effect of ozone cycling on other mask components, such as elastics. 

scholarly journals A Numerical Study of the Effect of Particle Size on Particle Deposition on Turbine Vanes and Blades

2021 ◽  
Vol 13 (5) ◽  
pp. 168781402110178
Author(s):  
Zhengang Liu ◽  
Weinan Diao ◽  
Zhenxia Liu ◽  
Fei Zhang
Keyword(s):  
Particle Size ◽  
Particle Deposition ◽  
Numerical Study ◽  
Stokes Number ◽  
Capture Efficiency ◽  
Particle Capture ◽  
Factors Affecting ◽  
Pressure Surface ◽  
Deposition Area ◽  
Turbine Vanes

Particle deposition could decrease the aerodynamic performance and cooling efficiency of turbine vanes and blades. The particle motion in the flow and its temperature are two important factors affecting its deposition. The size of the particle influences both its motion and temperature. In this study, the motion of particles with the sizes from 1 to 20 μm in the first stage of a turbine are firstly numerically simulated with the steady method, then the particle deposition on the vanes and blades are numerically simulated with the unsteady method based on the critical viscosity model. It is discovered that the particle deposition on vanes mainly formed near the leading and trailing edge on the pressure surface, and the deposition area expands slowly to the whole pressure surface with the particle size increasing. For the particle deposition on blades, the deposition area moves from the entire pressure surface toward the tip with the particle size increasing due to the effect of rotation. For vanes, the particle capture efficiency increases with the particle size increasing since Stokes number and temperature of the particle both increase with its size. For blades, the particle capture efficiency increases firstly and then decreases with the particle size increasing.

A multifunctional multi-walled carbon nanotubes/ceramic membrane composite filter for air purification

RSC Advances ◽  
2015 ◽  
Vol 5 (112) ◽  
pp. 91951-91959 ◽  
Author(s):  
Yang Zhao ◽  
Zhaoxiang Zhong ◽  
Ze-Xian Low ◽  
Zhong Yao
Keyword(s):  
Carbon Nanotubes ◽  
Ceramic Membrane ◽  
Small Diameter ◽  
Capture Efficiency ◽  
Air Purification ◽  
Particle Capture ◽  
Multi Walled Carbon Nanotubes ◽  
Composite Filter ◽  
Walled Carbon Nanotubes

Carbon nanotubes (CNTs) are very small diameter fibers that have the potential to be integrated into filters to further increase particle capture efficiency.

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