Diffusion predominates below the 0.1 μm diameter particle size, whilst impaction and interception predominate above 0.4 μm.[11] In between, near the most penetrating particle size (MPPS) 0.21 μm, both diffusion and interception are comparatively inefficient.[12] Because this is the weakest point in the filter’s performance, the HEPA specifications use the retention of particles near this size (0.3 μm) to classify the filter.[11]
From Wikipedia. This Wikipedia article actually seems pretty encouraging—despite 0.3 micrometers being near the filter’s weakest point, it still filters out 99.95% of those particles?
If most transmission takes place over ~2 meters, it could be very helpful to install HEPA filters near e.g. hospital desks/beds/doorways. I don’t remember observing ventilation ducts near desks/beds/doorways in the hospitals I’ve visited.
From Wikipedia. This Wikipedia article actually seems pretty encouraging—despite 0.3 micrometers being near the filter’s weakest point, it still filters out 99.95% of those particles?
If most transmission takes place over ~2 meters, it could be very helpful to install HEPA filters near e.g. hospital desks/beds/doorways. I don’t remember observing ventilation ducts near desks/beds/doorways in the hospitals I’ve visited.