How can masks possibly work? Viruses are tiny!
This awesome video explains how the mask fabric, made up of multiple layers of sticky, electrically-charged, randomly oriented fibres works so well. GO WATCH IT. But if you are boycotting YouTube, here’s a summary of the physics of stopping particles:
- Very small particles like to stick to things. This means that if a particle touches a fibre, it’s going to stay stuck to it.
- Masks have an electric charge that attracts aerosols. The physics is more complicated than I want to go into, but this article (2022-01-28, paywalled, sorry) explains how the electric attraction in N95 masks work.
- Masks have many layers of fibres which are arranged randomly. This means that to get through, the aerosols would have to move in twisty-turny paths to get past all the fibres. 1) aerosols move in pretty straight lines and 2) the fibres actually attract the particles, see above.
I personally don’t worry more about handling my mask than I worry about handling my shirt, shoes, glasses, hat, etc. I figure that most of the particles are going to be on the inside of the mask, not on the surface that I touch.
Additional Factors
In addition to the physics of the mask fibres, there are some helpful things the awesome video doesn’t talk about:
- Masks don’t have to stop all the virus to help. The more virus particles you are exposed to, the sicker you get. Thus, if a mask keeps a lot of the particles from going out / coming in, even if it is not all, that’s a win!
- Humidity helps. There are a number of papers I have read that say that respiratory viruses are sensitive to humidity. One thing I’ve read is that when the air is drier, the droplets you expel evaporate faster, making them smaller, making it easier for them to surf on air currents and stay in the air. Another is that your respiratory tract doesn’t do as good a job of conveyor-ing out junk when it’s dry. Well, when you wear a mask, the humidity of what you inhale and exhale goes up. Maybe this makes your respiratory tract work better and you produce more droplets and fewer aerosols. (Note: this is my theory, I’ve never heard anyone else float this theory. I could be wrong.)
- Masks change the breath direction. When you talk to a friend without wearing a mask, your breath goes forwards, right towards whoever you are talking to. When you are wearing a mask, even if the air leaks out the sides, it is no longer going forwards: it’s going up or backwards, not towards your friend. (Watch this video of a woman exhaling smoke through various masks.)
- Masks slow breath down. When your breath is redirected through the top or sides of a mask, it slows down. The slower that particles go, the more they will fall to the ground. (Hopefully. This is another theory of mine only and I could be wrong.)
- Masks are more effective when the contagious people wear them. Masks work best when the droplets are big, and the droplets are biggest right when they come out of your mouth/nose.
I don’t know if ether is a good proxy for COVID-19 or not, but this video of someone shooting ether through a mask / no mask to how far it travels is entertaining, at least!
Scientific Modelling
Here are some papers which talk about measurements of aerosols or which do mathematically modelling of virus dispersion with and without masks:
- This paper (2021-12-02) says that if two people are speaking, one infected and one not, at a distance of 1.5m:
- If neither is wearing a mask, the susceptible person is 90% likely to get infected after just a few minutes.
- If the infected person is wearing a surgical mask and the susceptible person is not wearing a mask, the susceptible person won’t hit the 90% likely threshold until 30 minutes.
- If the infected person is wearing a FFP2 mask and the susceptible person is not wearing a mask, the susceptible person will only be 20% likely to be infected after until 60 minutes.
- If both people are wearing surgical masks, the susceptible person will be under 30% likely to be infected after 60 minutes.
- If both people are wearing FFP2 masks, the susceptible person will be under 0.4% likely to be infected after 60 minutes.
- This paper (2021-05-20) says that not every exhaled particle has a virus in it, and that in most environments, there are few enough that a surgical mask can deflect enough that a surgical mask is usually good enough. (For hospitals, or arguing nose to nose with an anti-vaxxer, you ought to have an FFP2.)
- This paper (2024-04-25) reports that the higher the CO2 concentration, the more stable SARS-CoV-2 virus particles are.