Measurement of filtration efficiencies of healthcare and consumer materials using modified respirator fit tester setup

Abstract

During the current SARS-CoV-2 pandemic there is unprecedented demand for personal protective equipment (PPE), especially N95 respirators and surgical masks. The ability of SARS-CoV-2 to be transmitted via respiratory droplets from asymptomatic individuals has necessitated increased usage of both N95 respirators in the healthcare setting and masks (both surgical and homemade) in public spaces. These precautions rely on two fundamental principles of transmission prevention: particle filtration and droplet containment. The former is the focus of NIOSH N95 testing guidelines, and the latter is an FDA guideline for respirators and surgical masks. While studies have investigated droplet containment to provide guidance for homemade mask production, limited work has been done to characterize the filtration efficiency (FE) of materials used in home mask making. In this work, we demonstrate the low-cost (<$300) conversion of standard equipment used to fittest respirators in hospital and industrial settings into a setup that measures quantitative FEs of materials based on NIOSH N95 guidelines, and subsequently measure FEs of materials found in healthcare and consumer spaces. These materials demonstrate significant variability in filtration characteristics, even for visually similar materials. We demonstrate a FE of 96.49% and pressure drop of 25.4 mmH 2 0 for a double-layer of sterilization wrap used in surgical suites and a FE of 90.37% for a combination of consumer-grade materials. The excellent filtration characteristics of the former demonstrate potential utility for emergent situations when N95 respirators are not available, while those of the latter demonstrate that a high FE can be achieved using publicly available materials.

Risks posed by SARS‐CoV‐2 to North American bats during winter fieldwork

“…The viral emission rate for infected humans ( Q I ) was estimated from models of respiration (Buonanno, Stabile, & Morawska, 2020,Buonanno, Morawska, & Stabile, 2020) and inference from a documented super spreading event (Miller et al, 2020). The effectiveness of face coverings in reducing emission, including N95 masks, surgical masks, cloth masks, and face shields, was estimated from studies that quantified the filtration efficiencies (Davies et al, 2013; Lindsley et al, 2014; Long et al, 2020). The typical sensitivity and sensitivity of RT‐PCR tests for SARS‐CoV‐2 were estimated from several meta‐analyses of current tests (Arevalo‐Rodriguez et al, 2020; Watson et al, 2020).…”

A reusable, locally manufactured, half- face respirator provides better protection than fitted disposable N95 masks: development and quantitative fit-testing comparison

“…The use of the sterilization wrap as expiratory filter material is appropriate since they are readily available in the hospital setting. Moreover, the Halyard (H100) sterilization wrap has been shown to have a particle filtration efficiency (PFE 79.8%) comparable to the standard hospital surgical mask (PFE 74.4%) 26 . The unidirectional air flow reduces moisture build-up and contamination of the inspiratory filters potentially prolonging their life.…”

Are surgical masks manufactured from sterilisation wrap safe?

“…Three further studies have reported on sub-micron filtration in their prototypes. Long et al detail a filtration efficiency of 96.5% with two layers of H500 wrap [17]. Meijer et al claim a filtration efficiency of 93.8% through three layers of Halyard H300, whilst Walawalkar et al report an efficiency of 92.1% through two layers [18,19].…”