COVID-19: Smoke Testing of Surgical Mask and Respirators

Background: Fluid Resistant Surgical Masks have been implemented in UK personal protective equipment (PPE) guidelines for COVID-19 for all care sites that do not include aerosol-generating procedures (AGPs). FFP3 masks are used in AGP areas. Concerns from the ENT and plastic surgery communities out with intensive care units have questioned this policy. Emerging evidence on cough clouds and health care worker deaths has suggested that a review is required.

Aims: To test the efficacy of Fluid Resistant Surgical Mask with and without adaptions for respiratory protection. To test the efficacy of FFP and FFP3 regarding fit testing and usage.

Methods: A smoke chamber test of 5 min to model an 8-h working shift of exposure while wearing UK guideline PPE using an inspiratory breathing mouthpiece under the mask. Photographic data were used for comparison.

Results: The Fluid Resistant Surgical Mask gave no protection to inhaled smoke particles. Modifications with tape and three mask layers gave slight benefit but were not considered practical. FFP3 gave complete protection to inhaled smoke but strap tension needs to be 'just right' to prevent facial trauma. Facial barrier creams are an infection risk.

Conclusions: Surgical masks give no protection to respirable particles. Emerging evidence on cough clouds and health care worker deaths suggests the implementation of a precautionary policy of FFP3 for all locations exposed to symptomatic or diagnosed COVID-19 patients. PPE fit testing and usage policy need to improve to include daily buddy checks for FFP3 users.