Procedural and surgical masks; the goal of those is really to prevent large droplets from falling on to the healthcare providers’ mucous membranes.
So nose, mouth, mucous membranes, eyes although the mask doesn’t do that you need to wear eye protection with it.
There’s not really a strong seal around it which is fine as the goal is to catch the droplets.
The N95 respirator on the other hand needs to have a tight seal, and it needs to be fitted to the individual, which is why we do fit testing. Each time that you use it it needs to have a seal check to make sure that that seal works. And you know change and weight change and facial hair all of these things can change that seal. So through your lifetime we need to check those seal checks and and fit testing every couple of years, because our bodies and our face faces change.
So a surgical mask or procedure mask would be indicated when you’re concerned about a viral respiratory illness in general. So we wear it for influenza or for rhinoviruses or any of the common seasonal viruses that circulate. It’s not stand alone we also need a protection and prescription eye not adequate, you need to wear either protective goggles or a visor, or some of the surgical or procedural masks have visors that are built-in.
And together with gloves and gown for the contact component of it.
Respirators are worn for a very specific number of diseases where there’s an airborne transmission component, and the list is actually very small, it’s varicella or chickenpox or disseminated zoster which is also sort of like the second time to get chickenpox, but in a disseminated fashion. Tuberculosis, measles and then there’s some rare emerging diseases where it’s recommended, although the science isn’t clear whether it’s absolutely needed.