Epistemic status: Pretty confident, seems obviously correct.
Summary: We should promote widespread use of reusable silicone masks to stop the spread of SARS-CoV-2.
Masks and transmission of SARS-CoV-2
SARS-CoV-2 spreads mainly through respiratory droplets. Most of the discussion of mask usage to prevent transmission has so far been centered on surgical masks and disposable filtering facepiece particle (FFP) masks (also called respirators sometimes). Surgical masks do not form an airtight seal to the face and thus can't reliably prevent transmission. Achieving a tight fit with FFP masks is tricky and at least requires some practice. A recent post on LessWrong suggested the use of reusable masks with replaceable filters and body made out of silicone, such as this:
(North 7700 Series Half Mask Air-Purifying Respirator / PD-USGOV-HHS-CDC)
These masks (also sometimes called respirators) are available in different sizes and can be equipped with filters of N99 / P3 standard. Safe usage should be much easier to achieve than with FFP masks due to the mask body having a flexible silicone edge that can form a tight seal with the face. Additionally, they are equipped with one-way valves that prevent the filters from being soaked by the wearers' breath. They are more expensive than the other mask types (~50$), but can be easily mass-produced using injection molding. Thus, widespread use of such masks seems highly desirable and might play a big part in reducing effective transmission rates without requiring severe social-distancing measures. Compared to the economic costs of these measures, the cost of providing these masks to everyone, at least in industrialized countries, seems to be negligible. (Much more detail can be found in the previously mentioned post.)
Call to action
Given the plausibility and potential benefit of the idea described above, it is urgent that we take action to promote it or figure out if it is wrong. I strongly encourage the readers of this post to:
- Share the idea widely and try to convince influential people.
- Buy a mask for yourself, friends, and family; wear them when you're in public (or generally close to people that you don't live with) to protect yourself and others and increase social acceptance.
- Use 3D printers and share potential designs; distribute self-made masks to people in need of protective equipment.
- Reach out to groups which are at high risk of infections and with an interest in protecting themselves (e.g. nurses in nursing homes).
- Suggest further ideas and point out potential problems in the comments.
I bought a half-mask and several filters almost two months ago, and it's definitely easier and safer for my once-per-week shopping trip than a single use mask. I don't think that it's a particularly effective general solution though, for the following reasons:
1. All of these are sold out. To make more, you need to manufacture both masks and filters.
2. All the replaceable filters are sold out. The filters need to be sequentially rotated or otherwise disinfected.
3. Wearing one for anything more than 30 minutes is still quite awful.
4. Most of them have exhaust valves which still spread the virus to others.
Pretty sure. You should not get your filter wet though since this may allow diffusion across the filter, which is why it is unsafe to wear (N 95 or other) fleece masks for extended periods. Also stuff that is bound in the filter is also attracted via Van-der-Waals forces which are really strong on this scale.