Filter quality of electret masks in filtering 14.6–594 nm aerosol particles: Effects of five decontamination methods

Abstract

This study investigates the effects of five decontamination methods on the filter quality (qf) of three commercially available electret masks—N95, Gauze and Spunlace nonwoven masks. Newly developed evaluation methods, the overall filter quality (qf,o) and the qf ratio were applied to evaluate the effectiveness of decontamination methods for respirators. A scanning mobility particle sizer is utilized to measure the concentration of polydispersed particles with diameter 14.6–594 nm. The penetration of particles and pressure drop (Δp) through the mask are used to determine qf and qf,o. Experimental results reveal that the most penetrating particle size (MPS) for the pre-decontaminated N95, Gauze and Spunlace masks were 118 nm, 461 nm and 279 nm, respectively, and the respective penetration rates were 2.6%, 23.2% and 70.0%. The Δp through the pretreated N95 masks was 9.2 mm H2O at the breathing flow rate of heavy-duty workers, exceeding the Δp values obtained through Gauze and Spunlace masks. Decontamination increased the sizes of the most penetrating particles, changing the qf values of all of the masks: qf fell as particle size increased because the penetration increased. Bleach increased the Δp of N95, but destroyed the Gauze mask. However, the use of an autoclave reduces the Δp values of both the N95 and the Gauze mask. Neither the rice cooker nor ethanol altered the Δp of the Gauze mask. Chemical decontamination methods reduced the qf,o values for the three electret masks. The value of qf,o for PM0.1 exceeded that for PM0.1–0.6, because particles smaller than 100 nm had lower penetration, resulting in a better qf for a given pressure drop. The values of qf,o, particularly for PM0.1, reveal that for the tested treatments and masks, physical decontamination methods are less destructive to the filter than chemical methods. Nevertheless, when purchasing new or reusing FFRs, penetration should be regarded as the priority.

Effect of various decontamination procedures on disposable N95 mask integrity and SARS-CoV-2 infectivity

“…In order to be compatible with reuse, methods of N95 mask SARS-CoV-2 decontamination must remove the viral threat, be harmless to the mask user, and not compromise the integrity of the various mask elements. The decontamination methods utilized, 70% ethanol, ultraviolet light, and vaporized hydrogen peroxide, have previously been demonstrated to be safe for mask users (3)(4)(5)9). We found that any ethanol exposure significantly altered mask integrity, as previously reported (7).…”

“…This team was tasked with determining feasibility of mask decontamination within our health system. Prior studies have investigated how decontamination procedures, including ethanol, ultraviolet light, and vaporized hydrogen peroxide (VHP) alter N95 mask integrity (2)(3)(4)(5)(6)(7)(8), but it is unclear how effective these sterilization procedures are at destroying SARS-CoV-2. Here we investigate the effect of different decontamination methods on disposable N95 mask integrity and on removing the infectious potential of SARS-CoV-2.…”

Relative survival of Bacillus subtilis spores loaded on filtering facepiece respirators after five decontamination methods

“…Both sides of each N95 FFR were exposed for different times ‐ 1, 2, 5, 10 and 20 minutes ‐ in a BSC. The UV intensity was measured using a handheld laser power and energy meter (OPHIR NOVAII, model Nova II PD300‐UV) and was reported as a mean of five measurements over a 10 × 10 mm aperture with a swivel mount and a removable filter. Autoclave: The N95 FFR was heated for 15 minutes at 121°C and 103 kPa. TERC: The N95 FFR was placed in an electric rice cooker for dry heating for 3 minutes (149‐164°C, without added water) …”

“…TERC is frequently used in hospitals in Taiwan . The filter quality of FFRs, including particle penetration and pressure drop, was originally published elsewhere …”

Pneumask: Modified Full-Face Snorkel Masks as Reusable Personal Protective Equipment for Hospital Personnel

“…Besides autoclaving, the mask may be immersed in a bath of bleach for decontamination [12]. Thus, we tested whether a mask could survive the relatively harsh chemical conditions of immersion in a bath of bleach.…”