Filtration Efficiency, Breathability, and Reusability of Improvised Materials for Face Masks

There is paucity of data on the performance of different improvised materials to cope with the COVID-19 pandemic. The goal of this study is to evaluate the filtration efficiency and breathability of improvised filtration and commonly available mask materials, as well as to assess their reusability. Materials readily available to the general public such as cotton, fragrance and additive-free dry baby cleaning wipes, and those abundantly available in the hospital setting, such as sterilization wraps, were chosen for testing, amongst others. In the COVID-important 2–5 m particle range, two-layers of cotton provided filtration efficiency between 34%–66%. Amongst potential filter materials, 300-weight sterilization wraps provided approximately 80% filtration efficiency and are readily available in the healthcare setting. The addition of sterilization wrap to cotton fabrics brought the filtration efficiency to above that of the sterilization wrap (80%-90%) at the expense of added pressure drop. Four-layers of dry baby wipes performed very well with a filtration efficiency of 85% and a reasonable pressure drop (1/3 of procedure mask). Since the material is advertised as pure spunlace polypropylene and designed to contact the skin during cleaning, it would appear generally safe as a filter insert. Of improvised filters, polypropylene electrostatic HVAC filters performed the best with filtration efficiencies of >99%, but are not recommended due to the risk of confusion with glass-based HVAC filters and uncertainty regarding trace materials used in the filter. The filtration efficiency of two-layers of cotton fabrics with one-layer of sterilization wrap slightly improved over 10 laundry cycles, while the performance of other non-wovens, like dry baby wipes, degraded more rapidly and should be considered disposable. In summary, we found that a two-layer cotton fabric can provide a comfortable, breathable and reusable option. The addition of a sterilization wrap or four-layers of pure spunlace fragrance free dry baby wipes can significantly improve filtration and block expiratory aerosols at the expense of an added pressure drop.

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Characterization of glass fiber felt and its performance as an air filtration media

Journal of Industrial Textiles ◽

10.1177/1528083720961410 ◽

2020 ◽

pp. 152808372096141

Author(s):

Chi Zou ◽

Yunlong Shi ◽

Xiaoming Qian

Keyword(s):

Pressure Drop ◽

Glass Fiber ◽

Separation Efficiency ◽

Theoretical Calculations ◽

Filtration Efficiency ◽

Air Filtration ◽

Slow Increase ◽

Filter Materials ◽

Fine Fiber

The glass fiber felt made through flame blowing process was characterized on morphology and its filtration performance. Fiber diameter has been measured through SEM and BET methods. Theoretical calculations on pressure drop and filtration efficiency were developed and compared with the experimental measurement. The discrepancy between the calculated results and measurement on filtration efficiency is derived from the presence of fine fiber (<0.5µm) in the glass fiber felt, which contributes to the actual high filtration efficiency in measurement. The multiple micro-layered structure in glass fiber felt, which improves the dust holding capacity and enables glass fiber felt as a depth filter. Glass fiber felt showed a longer duration of the slow increase region for pressure drop build-up comparing to other filter materials with lower averaged pressure drop through its filtration service life. Furthermore, quality factor calculation has been developed for prediction on the energy cost performance of the filters based on the pressure drop, separation efficiency and dust holding capacity.

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Pressure drop in selected porous materials used for thermal regenerators

Cryogenics ◽

10.1016/0011-2275(80)90094-6 ◽

1980 ◽

Vol 20 (10) ◽

pp. 587-591 ◽

Cited By ~ 4

Author(s):

H. Appel ◽

F.X. Eder

Keyword(s):

Pressure Drop ◽

Porous Materials ◽

Materials Used

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Approximate pressure drop and filtration efficiency expressions for semi-open wall-flow channels

The Canadian Journal of Chemical Engineering ◽

10.1002/cjce.21982 ◽

2014 ◽

Vol 92 (9) ◽

pp. 1517-1525 ◽

Cited By ~ 9

Author(s):

Onoufrios Haralampous ◽

Theodore Kontzias

Keyword(s):

Pressure Drop ◽

Filtration Efficiency ◽

Flow Channels ◽

Wall Flow

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The protective performance of reusable cloth face masks, disposable procedure masks, KN95 masks and N95 respirators: Filtration and total inward leakage

PLoS ONE ◽

10.1371/journal.pone.0258191 ◽

2021 ◽

Vol 16 (10) ◽

pp. e0258191

Author(s):

Scott Duncan ◽

Paul Bodurtha ◽

Syed Naqvi

Keyword(s):

Geometric Mean ◽

Particle Diameter ◽

Standing Position ◽

Filtration Efficiency ◽

Protection Factor ◽

Respiratory Illnesses ◽

Particle Penetration ◽

Preventive Health Measure ◽

Materials Used ◽

N95 Respirators

Face coverings are a key component of preventive health measure strategies to mitigate the spread of respiratory illnesses. In this study five groups of masks were investigated that are of particular relevance to the SARS-CoV-2 pandemic: re-usable, fabric two-layer and multi-layer masks, disposable procedure/surgical masks, KN95 and N95 filtering facepiece respirators. Experimental work focussed on the particle penetration through mask materials as a function of particle diameter, and the total inward leakage protection performance of the mask system. Geometric mean fabric protection factors varied from 1.78 to 144.5 for the fabric two-layer and KN95 materials, corresponding to overall filtration efficiencies of 43.8% and 99.3% using a flow rate of 17 L/min, equivalent to a breathing expiration rate for a person in a sedentary or standing position conversing with another individual. Geometric mean total inward leakage protection factors for the 2-layer, multi-layer and procedure masks were <2.3, while 6.2 was achieved for the KN95 masks. The highest values were measured for the N95 group at 165.7. Mask performance is dominated by face seal leakage. Despite the additional filtering layers added to cloth masks, and the higher filtration efficiency of the materials used in disposable procedure and KN95 masks, the total inward leakage protection factor was only marginally improved. N95 FFRs were the only mask group investigated that provided not only high filtration efficiency but high total inward leakage protection, and remain the best option to protect individuals from exposure to aerosol in high risk settings. The Mask Quality Factor and total inward leakage performance are very useful to determine the best options for masking. However, it is highly recommended that testing is undertaken on prospective products, or guidance is sought from impartial authorities, to confirm they meet any implied standards.

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Antimicrobial nanoparticle-coated electrostatic air filter with high filtration efficiency and low pressure drop

The Science of The Total Environment ◽

10.1016/j.scitotenv.2015.07.003 ◽

2015 ◽

Vol 533 ◽

pp. 266-274 ◽

Cited By ~ 28

Author(s):

Kyoung Mi Sim ◽

Hyun-Seol Park ◽

Gwi-Nam Bae ◽

Jae Hee Jung

Keyword(s):

Pressure Drop ◽

Low Pressure ◽

Filtration Efficiency ◽

Air Filter

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Experimental measurement of the filtration efficiency and pressure drop of wall-flow diesel particulate filters (DPF) made of biomorphic Silicon Carbide using laboratory generated particles

Applied Thermal Engineering ◽

10.1016/j.applthermaleng.2017.11.149 ◽

2018 ◽

Vol 131 ◽

pp. 41-53 ◽

Cited By ~ 19

Author(s):

M. Pilar Orihuela ◽

Aurora Gómez-Martín ◽

Paolo Miceli ◽

José A. Becerra ◽

Ricardo Chacartegui ◽

...

Keyword(s):

Silicon Carbide ◽

Pressure Drop ◽

Experimental Measurement ◽

Filtration Efficiency ◽

Diesel Particulate ◽

Diesel Particulate Filters ◽

Particulate Filters ◽

Wall Flow

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Filtration efficiency and pressure drop modelling of particulate filters with rear plug damage

International Journal of Engine Research ◽

10.1177/1468087420916679 ◽

2020 ◽

pp. 146808742091667

Author(s):

Onoufrios Haralampous ◽

Marios Mastrokalos ◽

Fotini Tzorbatzoglou ◽

Chris Dritselis

Keyword(s):

Steady State ◽

Pressure Drop ◽

Filtration Efficiency ◽

Driving Cycle ◽

Ceramic Filter ◽

Particulate Filter ◽

Local Pressure ◽

Particulate Filters ◽

Pressure Loss Coefficient ◽

Particulate Mass

A model suitable for wall-flow particulate filters with partial rear plug damage is developed and experimentally validated in this work. A ceramic filter with 16% of the rear plugs mechanically removed is tested at steady-state conditions on the engine bench and transient driving cycle conditions on the chassis dynamometer. After decanning of the monolith, destructive analysis is conducted to identify deposit loading variations and scanning electron microscopy is used to study the deposit structures in the channels. It is shown that channels without rear plugs develop distinct deposit structures in the entry zone. Hence, a local pressure loss coefficient is applied to model the effect of entrance flow constrictions, taking also into account deposit restructuring phenomena at higher flow rates. In addition, a deep-bed filtration submodel is used to capture the effect of non-uniform wall velocities on deposit accumulation in the wall. The modified model is first fitted to the engine bench data and then validated in a wider range of conditions using the driving cycle tests. With the exception of prolonged steady-state loading conditions, good pressure drop and filtration efficiency predictions are obtained throughout the tests in conjunction with correct deposit property profiles. Notably, the cold-start worldwide harmonized light vehicles test cycle shows that the current European on-board diagnosis threshold limit for particulate mass is too relaxed to trigger a malfunction indication for moderate filter faults. In conclusion, the model can be applied in damaged particulate filter studies for the assessment of leaked particulate mass, the specification of more effective legislation limits and the development of rigorous on-board diagnosis systems and algorithms.

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Design and Evaluation of Spinneret Module with Line-Type and Multi-Holes of Electro-Spun

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.311.243 ◽

2013 ◽

Vol 311 ◽

pp. 243-248

Author(s):

Wei Cheng Chu ◽

Chin Pan Huang ◽

Tien Wei Shyr ◽

Li Chou Chen ◽

Shu Ping Chiu

Keyword(s):

Pressure Drop ◽

Production Line ◽

Fiber Diameter ◽

Filtration Efficiency ◽

Gray Level ◽

Average Fiber Diameter ◽

Sampling Area ◽

Composite Nonwoven ◽

Line Type

For the wide application in the field of filtration and bio-medicine, the purpose of this study is to design a spinneret module of electro-spun which can produce composite nonwoven with sub-micrometer fiber continually. Applying the principle of melt-blown, a spinneret module with line-type and multi-holes which was assembled with small beads and filtering net, was designed. In order to construct a continual electro-spun production line, a traversal device was designed to control the traverse-motion of spinneret module for the even lapping and a stainless plate was adopted as collecting plate. In condition of 41KV working voltage, 0.3573 mL/min throughput and 42cm CSD (Capillary-Screen-Distance), a continual PEO nonwoven can be produced with average fiber diameter of 576nm and of CV% 13.4%. To a sampling area of 10cm×10cm and basis weight of 7.257 g/m2 electro-spun nonwoven, the CV% of gray level of its image is 2% and its filtration efficiency is up to 91.2% with pressure drop 13.8mm-H20 by TSI 8130 (32LPM, 5% NaCl).

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A problem-solving routine for improving hospital operations

Journal of Health Organization and Management ◽

10.1108/jhom-09-2013-0191 ◽

2015 ◽

Vol 29 (2) ◽

pp. 252-270 ◽

Cited By ~ 6

Author(s):

Manimay Ghosh ◽

Durward K Sobek II

Keyword(s):

Problem Solving ◽

Process Improvement ◽

Hospital Setting ◽

Improve Patient Care ◽

Healthcare Setting ◽

Theory Approach ◽

Structured Interviews ◽

Short Term ◽

Content Type ◽

Hospital Operations

Purpose – The purpose of this paper is to examine empirically why a systematic problem-solving routine can play an important role in the process improvement efforts of hospitals. Design/methodology/approach – Data on 18 process improvement cases were collected through semi-structured interviews, reports and other documents, and artifacts associated with the cases. The data were analyzed using a grounded theory approach. Findings – Adherence to all the steps of the problem-solving routine correlated to greater degrees of improvement across the sample. Analysis resulted in two models. The first partially explains why hospital workers tended to enact short-term solutions when faced with process-related problems; and tended not seek longer-term solutions that prevent problems from recurring. The second model highlights a set of self-reinforcing behaviors that are more likely to address problem recurrence and result in sustained process improvement. Research limitations/implications – The study was conducted in one hospital setting. Practical implications – Hospital managers can improve patient care and increase operational efficiency by adopting and diffusing problem-solving routines that embody three key characteristics. Originality/value – This paper offers new insights on why caregivers adopt short-term approaches to problem solving. Three characteristics of an effective problem-solving routine in a healthcare setting are proposed.

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