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Recovery of Bacteria in Filtering Facepiece Respirators and Effects of Artificial Saliva/Perspiration on Bacterial Survival and Performance of Respirators

Category: Bioaerosols

Volume: 17 | Issue: 1 | Pages: 187-197
DOI: 10.4209/aaqr.2015.03.0196
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Tzu-Hsien Lin1, Feng-Cheng Tang2, Chia-Hsiu Chiang3, Cheng-Ping Chang4,5, Chane-Yu Lai 3,6

  • 1 Department of Dental Hygiene China Medical University, Taichung, Taiwan
  • 2 Department of Occupational Medicine, Changhua Christian Hospital, Changhua, Taiwan
  • 3 Department of Occupational Safety and Health, Chung Shan Medical University, Taichung, Taiwan
  • 4 Institute of Occupational Safety and Health, Ministry of Labor, New Taipei, Taiwan
  • 5 Department of Occupational Safety and Health, Chang Jung Christian University, Tainan, Taiwan
  • 6 Department of Occupational Medicine, Chung Shan Medical University Hospital, Taichung, Taiwan

Highlights

Survival of bacteria on filtering facepiece respirators (FFRs) tested to 96-hr storage.
The worst case with highest relative survival (RS) occurred at 37°C and 95% RH.
N95 added with artificial perspiration, RS increased by over 100% after 8-hr storage.
Surgical mask added with artificial saliva, RS became over 100% after 8-hr storage.
Loading of bacteria increased the penetration and filter quality factor of FFRs.


Abstract

This study seeks the optimal method for recovering loaded bacteria from filtering facepiece respirators (FFRs) and investigates the effects of artificial saliva (AS), artificial perspiration (AP) and storage conditions on the survival of bioaerosols and the filter performance of FFRs. Bioaerosols were generated using a Collison nebulizer in a test system and loaded on either N95 or surgical masks. Elution using centrifuge at 3500 rpm for ten min followed by vortexing for one min yielded a high relative survival (RS) rate of airborne Bacillus subtilis (BS) spores. When AS was added to the N95 FFR, the RS of BS declined during the first eight hours of storage and then increased to reach its highest value after 24 hr of storage. The worst case with the highest RS was at 37°C and 95% RH (p < 0.001). When AP was added to the N95 FFR and stored under the worst conditions, RS increased by over 100% during eight hours of storage. When AS was added to a surgical mask, the RS also increased by over 100% in eight hours of storage, but when AP was added to the surgical mask, RS immediately declined. When Escherichia coli (EC) were tested, their RS was lower than those of the BS samples. (Following loading with bacteria, the particle penetration and filter quality factor (qf) increased (p < 0.001) but the slope of the linear regression between the pressure drop (∆p) and the flow rate through the filter was not statistically significantly changed (p = 0.233). In conclusion, AS and AP increased the survival of BS; AP was especially effective in N95 masks and AS was especially effective in surgical masks.

Keywords

Respirator Bioaerosols Filtration Personnel protection Respiratory health


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