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

Abstract

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.

A Simple Method to Quantify Outward Leakage of Medical Face Masks and Barrier Face Coverings: Implication for the Overall Filtration Efficiency

“…In agreement with that observation, the results of the present study indicated that mask breathability has a major consistent effect on leak performance, as masks with high breathability showed markedly less leakage. This is also in agreement with that recently reported by Duncan et al, suggesting that a high pressure drop may be partially responsible for mask leakage at least during exhalation [ 44 ]. Our work not only confirmed this hypothesis, but evidenced that high breathability can drastically limit the mask leakage, facilitating the passage of the airflow through the mask filter also when the face fit is not optimized.…”

“…Nonetheless, the fraction of air leaking from the face seal plays a key role in the overall filtration efficiency and has an impact also on the whole mask breathability. In their recent work, Duncan and co-workers demonstrated the importance of the inward leakage in the protection efficiency of a mask and how this is influenced by the mask fit [ 44 ]. In the present study we measured the outward leakage on some typical community and surgical masks, providing a simple method for a quantitative estimation of the flow repartition at realistic flow rates.…”

Characterization of DELUX: Ultraviolet light sterilization device for PFF2 / N95 masks against COVID-19

“…La línea negra suaviza los puntos (FFT). La línea verde continua es el ajuste monoexponencial de la data experimental, la emisión de la lámpara UVC alcanza un valor máximo de 25 mW luego de 400 s. Potencia mínima emitida ∼8 mW La eficiencia de la esterilización también depende de la regularidad y el área expuesta en la superficie del material, ya que existe una dosis mínima de radiación UVC para desactivar los microorganismos [20,21], [28,29]. Por lo tanto, una esterilización exitosa ocurrirá solamente si toda la superficie del material está expuesta a la radiación UVC, porque cualquier sombra producida por las capas de tela de las máscaras puede reducir la efectividad de la esterilización.…”

“…La dosis entre 0,5 y 1,8 J/cm 2 fue capaz de desactivar 99,9 % de los patógenos, tales como algunos tipos de Influenza A, MERS-CoV, SARS-CoV y el bacteriófago MS2. La capacidad de filtrado de la máscara se mantuvo aún con dosis altas de radiación UVC [20,21], [28][29][30][31].…”

“…En este contexto, el Instituto Brasileño para la Seguridad del Paciente (IBSP) advierte que estas máscaras se mantienen efectivas cuando se utilizan hasta ocho horas consecutivas [19]. Las máscaras PFF2/N95 están formadas por capas superpuestas de polipropileno de tela no tejida (TNT), que filtran el aire y atrapan partículas en el orden de 0,3 µm, incluyendo microorganismos tales como el virus SARS-CoV-2 [20].…”