An N95 respirator (also named filtering facepiece respirators, FFRs) is a type of disposable, negative-pressure, and air-filtering facepiece mask with or without filtering valve. In contrast to cartridge-based elastomeric half-mask respirators or powered air-purifying respirator (PAPR), the respirator under study is a kind of particulate-filtering tight-fitting facepiece masks that are specifically designed to provide a highly secure fit to the face and effectively filter out airborne particles [1, 2]. This respirator also meets the N95 classification set by the U.S. National Institute for Occupational Safety and Health (NIOSH) and can filter out at least 95% of airborne particles with a mass median aerodynamic diameter of 0.3 μm [2]. The World Health Organization and the Center for Disease Control and Prevention (CDC) mandatorily recommend healthcare professionals to wear N95 respirators in clinical settings to reduce the spread of infectious respiratory diseases during the aerosol-generating procedures [1, 3].
At the beginning of the ongoing COVID-19 pandemic, the supply of NIOSH-approved N95 respirator was insufficient worldwide. In this regard, the Food and Drug Administration has permitted the use of non-NIOSH-approved respirators with an Emergency Use Authorization (EUA). Non-NIOSH-approved N95 respirators must undergo testing (using the Protocol of STP-0059 similar to the NIOSH standard testing procedure) to ensure sufficient occupational protection [3].
Prior to the COVID-19 pandemic, the literature focused on several key aspects related to N95 respirator usage, including the user-seal-check, fit rate, and real-time leakage. Improper face-seal fit and failed user-seal-check of the N95 respirator led to leakage and thus failed to provide respiratory protection against particles or infectious respiratory diseases [4,5,6]. However, the quality of N95 respirators, specifically its filtration efficiency, is rarely reported. Filtration efficiency is the verification of the particles being captured by the fibrous filtration media of N95 respirators when in use; that is, an N95 respirator may fail to provide protection with a low filtration efficiency due to material quality despite its guaranteed proper face-seal fit. NIOSH has presented the test results of non-NIOSH-approved N95 respirators in a format of images that was unable to conduct any investigation and analysis. These valuable data deserve a transcription to a format that facilitates further statistical analysis.
The sampled respirators were tested by the National Personal Protective Technology Laboratory (NPPTL) under CDC in the United States. The NPPTL estimated only the particulate filtration efficiency of the respirator by using a modified test plan of TEB-APR-STP-0059, and the respirator samples were non-NIOSH approved ones. The NPPTL offers an assessment of the filtration efficiency of respirators certified by a foreign regulatory authority, apart from NIOSH. During the COVID-19 pandemic, such assessment was used to evaluate the filtration efficiency of non-NIOSH approved respirators. The study provides gathered and organized raw data obtained by the NPPTL on filtration efficiency, initial filter resistance, and leakage of N95 to increase the availability of data and enhance the interpretability of the assessment regarding the quality of protection imparted by non-NIOSH-approved N95 respirators. It helped to ensure that healthcare workers were provided with adequate respiratory protection despite the respirator shortage at that time [7].
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