Personal protective equipment does not sufficiently protect against virus aerosol unless combined with advanced air purification or ventilation techniques

Abstract

Background: Healthcare workers (HCWs) are at risk from nosocomial transmission of SARS-CoV-2 from virus laden aerosols. This study aimed to: 1) quantify the degree of protection from virus aerosol provided by different types of mask (surgical, N95, fit-tested N95) and personal protective equipment (PPE); 2) determine if the use of a portable HEPA filter can enhance the effectiveness of PPE; 3) determine the effectiveness of a decontamination shower to remove virus aerosol contamination of a HCW. Methods: Virus aerosol exposure experiments were conducted using bacteriophage PhiX174 (10^8 copies/mL). A HCW wearing PPE (mask, gloves, gown, faceshield) was exposed to nebulised viruses for 40mins in a sealed clinical room. After exiting, the HCW doffed PPE. Virus exposure was quantified via skin swabs applied to the face and nostrils, forearms, neck, and forehead. Experiments were performed with and without the presence of a portable HEPA filter (set to 470m3/hr). Findings: Swabs quantified significant virus exposure under the surgical and N95 mask. Only the fit-tested N95 resulted in lower virus counts compared to no mask control (p=0.027). Nasal swabs demonstrated very high virus exposure, which was not mitigated by the surgical or N95 masks, although there was a trend for the fit-tested N95 mask to reduce virus counts (p=0.058). The addition of HEPA filtration substantially reduced virus counts from all swab sites, and to near zero levels when combined with a fit-tested N95 mask, gloves, gown and faces shield. Virus counts were substantially reduced to near zero levels following a shower. Interpretation: These data demonstrate that quantitatively fit tested N95 masks combined with a HEPA filter can offer protection against high virus aerosol loads at close range and for prolonged periods of time. Skin contamination from virus aerosol can be effectively by removed by showering. Funding: Epworth Hospital Capacity Building Research Grant ID: EH2020-654