Pretty much all masks protect you to some extend, but the extend and the way in which they offer protection is different.

Surgical masks protect you from inhaling larger particles to some extend, but there’s large holes in it’s coverage, so you still basically get a bunch of contaminated air in, especially when spending time in a saturated room. What they do do however is prevent you from spraying droplets all over everyone near when you sneeze/cough/exhale, and that’s their main benefit. Protecting others from the bacteria and viruses in those droplets.

I think a study was done that indicated they make you about 30% less likely to get sick.

More highly rated masks (generally called respirators), will completely seal your mouth and nose (at least to a much greater extend than a surgical mask) and prevent bad stuff from coming in much better. Generally this is indicated in the form of a rating N95, N99, N100 (actually 99.97). And indicates what percentage of bad stuff the mask is likely to keep out. They’re less useful for protecting others, since there’s still some exhalation valve to get rid of excess air (still mostly same usefulness as surgical mask though).

Medical professionals generally want the N95 masks, but they’ll happily settle for just a surgical mask if that’s the only thing available.

Simply putting on a mask does a great deal to limit the spread of a virus you already have - you’re not spewing particles all over your environment due to respiration.

Simply putting on a mask does very little to keep you from getting sick, because you’re very unlikely to be following proper PPE donning/doffing procedures. Unless you your house set up as a “clean zone” with two rooms between it and the outside world - one for removing PPE, and one for putting PPE on - then it’s really not helping much for reducing your exposure.

It makes sense to me.

I don't think that's how things work. Infection is a probabilistic thing. Maybe you'll get infected and maybe you won't. A high quality mask properly fit and worn according to an exacting protocol will reduce your risk of infection by X. Compromising on any of those factors may mean your risk is only reduced by Y and Y is less than X, but that doesn't mean it's a complete waste to wear a mask without a clean room or without fitting.

In one of the articles linked in this thread there is a study showing mask usage in children is nearly as effective as intervention against flu as vaccines are. I only read the summary of that paper but I don't think the children are working with clean zones or following doffing procedures carefully.

The article does mention that the effectiveness of masks was greater along older children. To me, that connects with what I wrote earlier. The better you are about using your mask, and here I expect mask diligence comes with age, the better a result you will have, but something is still better than nothing.

Oh, so that's why every hospital room has an air sealed clean zone that medical professionals have to enter to put on ppe?

For those that don't know, this is sarcasm. Most ICUs don't have any sort of sealed off clean zone.

> Most ICUs don't have any sort of sealed off clean zone.

Right - most ICUs aren’t set up to handle infectious diseases.

Here’s the CDC recommendation on doffing procedure. Note the repeated mention of the “doffing area”: https://www.cdc.gov/vhf/ebola/hcp/ppe-training/n95Respirator...

They simply need masks to protect their patients. They can never be sure that they themselves are not infected, and they treat a lot of severly ill (non COVID-19) patients in hospitals. If they spread the virus, those patients are at very high risk.

If that were true, all the medical professionals in America would already be infected.

Proper use of PPE very much decreases your chances of infection.