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.
Highlights
Standard patient care requires sterilizing or disinfecting surgical equipment and reclaimed medical devices that are contaminated by infectious agents [1]
Most health authorities do not recommend the reuse of masks, but several users have attempted to use various simple methods to reclaim them to protect against noninfectious ambient particulate matter (PM)— PM2.5, PM1 or PM0.1
The filtering effectiveness of reclaimed filtering facepiece respirators (FFRs) and masks varies among brands and decontamination methods, so relevant results are applicable only to FFRs treated under the same conditions
Summary
Standard patient care requires sterilizing or disinfecting surgical equipment and reclaimed medical devices that are contaminated by infectious agents [1]. Those items do not include masks, which should not be reused under normal circumstances. Further tests must be performed to evaluate the filtration performance of filters before and after reclamation This investigation applied three types of disposable mask, N95 FFRs (Dust Respirator 8210; 3M, St. Paul, MN, N95), gauze double-layer electret masks (Gauze, commercialized type, China) and spunlace nonwoven masks (Spunlace, Oimo, Taiwan), all of which are frequently used, and which can be reused when hospitals in Taiwan have insufficient masks for frontline healthcare workers [4]
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