Mask brace from FixTheMask.com. This seals a surgical mask (comparable in performance to an N95 respirator, an ASTM Level 1 mask stops 95% of the challenge particles) around the nose and mouth to prevent air from going around the sides. This improves the protection enormously by forcing the air to go through rather than around the filter medium.
I think we would have lost far fewer people to Covid-19 had superior masks been used at the outset, and superior masks (at least in terms of fit, if not material) were used against the 1918 flu pandemic. The Durand hospital mask tied behind the head for a much better seal than the earloop masks in use today.
(Does not constitute engineering or OH&S advice.)