The Effect of Hypochlorous Acid on the Filtration Performance and Bacterial Decontamination of N95 Filtering Facemask Respirators


      • Numerous hospital disinfectants are known to affect N95 FFR filtration performance.
      • Hypochlorous acid spray does not affect N95 FFR material's filtration performance.
      • Soaking N95 FFRs in HOCl can achieve decontamination, but not HOCl spray.



      Stabilized Hypochlorous acid (HOCl) is increasingly used as a hospital disinfectant and antiseptic, yet its effect on N95 filtration facemask respirators (FFR) is unknown. These FFRs could also contribute to fomite-based transmission of nosocomial infections if worn for extended use between patient rooms.


      Filtration performance of N95 FFR fabric swatches was assessed after various levels of HOCl exposure. N95 swatches were then contaminated with 108 E. coli or 108 Staph aureus and treated with HOCl solution, 70% ethyl alcohol, or normal saline. Surviving bacterial numbers were assessed by plate counts.


      The size-dependent filtration efficiency of HOCl-sprayed N95 FFR fabric ranged from 96 to 100%, showing no significant change. Flow resistance testing revealed almost no change compared to control. Submersion in HOCl, but not spraying, had an excellent bactericidal effect on contaminated swatches.


      The role of the outer hydrophobic layer of N95 FFRs is discussed regarding the effects of HOCl on filtration and bacterial decontamination.


      N95 material, sprayed with or briefly submerged in HOCl, maintained its filtration function. HOCl delivery by spray pump, however, would not accomplish decontamination of extended use FFRs between patient encounters. HOCl submersion of intact FFRs, contaminated with various hospital pathogens, is worth further study.


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