Hygienic masks

Medical/anti-infectious masks

August 1, 2020 — September 20, 2021

Figure 1

This is not necessarily the same thing as particulate masks, at least as far as priorities. Obviously some masks filter both well, but the priorities may differ. For example, particulate masks have a release valve, which AFAICT is not ideal for protecting other people from me if I wear it, although of course, protecting yourself from disease with a mask is not valueless to others in that you cannot transmit a disease you do not have.

Jeremy Howard, Cloth masks can protect the wearer:

As we all know now, the science shows that DIY masks are particularly good at protecting those around you in case you’re infected with COVID-19. But that does’t mean that you ca’t do a lot to protect yourself too.

Unfortunately, many public health bodies still incorrectly claim that there is no evidence that DIY masks are useful at protecting the wearer. There’s actually plenty of evidence they can. Effective protection for the wearer of a mask depends on three critical things:

  • Material: does the mask filter particles of the appropriate sizes?
  • Fit: do particles squeeze in through the gaps of your mask?
  • Sanitation: can you clean and re-use the mask?

Much more useful summary and advice there, now published (Brooks 2021).

Figure 2

Fixthemask notes some bonus hacks, including using a rubber band to keep masks snug. If you do’t want to hunt for weird filter types on ebay, there is the smart air guide which ranks normal fabrics and household filters.

How to Double Mask Correctly covers double masking, the latest, low-lift version of mask upgrades.

Enough practicalities! Here, have some silly fashion! Facemasks of your face. Glowing masks that are fiber optic!

Why so much confusion around masks? Probably several reasons, but here is an interesting one: The 60-Year-Old Scientific Screwup That Helped Covid Kill documents the argument and confusion about what size particles can transmit viruses and the lineage of some cargo-cult science that helped the misunderstandings take too long to settle.

Vendors for masks? Many on etsy. Slightly more professional-looking, uglier ones at Top Masks. See also particulate mask vendors.

Figure 3

1 Particulate masks

i.e. against pollution. See particulate masks.

2 Efficacy

A difficult problem, due to the many confounders. At a population level, efficacy is unclear according to the best approximation to meta-reviews that can be contrived (Talic et al. 2021). Some studies report no effect for recent variants, which seems to be about the paucity of RCTs for this question. Certainly it is contentious (Vainshelboim 2021). Also there are some interesting decision theory angles (Muller 2021).

3 References

Abaluck, Kwong, Styczynski, et al. 2021. Impact of Community Masking on COVID-19: A Cluster-Randomized Trial in Bangladesh.” Science.
Arpino, Grossi, Cortellessa, et al. 2022. Risk of SARS-CoV-2 in a Car Cabin Assessed Through 3D CFD Simulations.” Indoor Air.
Brooks. 2021. Maximizing Fit for Cloth and Medical Procedure Masks to Improve Performance and Reduce SARS-CoV-2 Transmission and Exposure, 2021.” MMWR. Morbidity and Mortality Weekly Report.
Muller. 2021. Masks, Mechanisms and Covid-19: The Limitations of Randomized Trials in Pandemic Policymaking.” History and Philosophy of the Life Sciences.
Randall, Ewing, Marr, et al. 2021. How Did We Get Here: What Are Droplets and Aerosols and How Far Do They Go? A Historical Perspective on the Transmission of Respiratory Infectious Diseases.” Interface Focus.
Su, Peng, Liu, et al. 2021. Comparison of Effects of N95 Respirators and Surgical Masks to Physiological and Psychological Health Among Healthcare Workers: A Randomized Controlled Trial.” International Journal of Environmental Research and Public Health.
Talic, Shah, Wild, et al. 2021. Effectiveness of Public Health Measures in Reducing the Incidence of Covid-19, SARS-CoV-2 Transmission, and Covid-19 Mortality: Systematic Review and Meta-Analysis.” BMJ.
Vainshelboim. 2021. Retraction Notice to ‘Facemasks in the COVID-19 Era: A Health Hypothesis’ [Medical Hypotheses 146 (2021) 5].” Medical Hypotheses.
Wang, Chia C., Prather, Sznitman, et al. 2021. Airborne Transmission of Respiratory Viruses.” Science.
Wang, Wensi, Wang, Lai, et al. 2022. Evaluation of SARS-COV-2 Transmission and Infection in Airliner Cabins.” Indoor Air.