Determining the filtration efficiency of half-face medical protection mask (N99) against viral aerosol

Hospital-based outbreaks of severe acute respiratory syndrome (SARS) have once again highlighted the vulnerability of healthcare workers (HCWs). Use of personal respiratory protective equipment was the main method used by HCWs to avoid nosocomial transmission. This paper describes the technology used to evaluate the filtration efficiency of the half-face medical protection mask (N99), manufactured by Firmshield Biotechnology, against viral aerosol. Viral aerosol was generated and then sampled simultaneously with and without the test mask. This enables a percentage efficiency value to be calculated against test phage f2 aerosols (surrogates of viral pathogen aerosols). At the same time the mask filtration efficiency against NaCl particle aerosol was determined by use of TSI8130 equipment and face-fit factor was tested by use of TSI8020 equipment. The half-face medical protection mask (N99) evaluated by use of the viral aerosol had a filtration efficiency >99%. The mask filtration efficiency against NaCl particle aerosol was 99.634 ± 0.024% and it had a good face-fit factor. This half-face medical protection mask (N99) can protect the wearer from viral aerosol disease transmission. The test method can be used to assess filtration efficacy against viral aerosol of masks used for respiratory protection.