The UK Government (finally) recommends a “face covering” if you are on public transport or in shops and other enclosed spaces. In most other countries where lockdown is past, masks are the normal polite thing to do, and in some countries mandatory. Many of us have recognised the value for a while. They certainly don’t replace social distancing and washing hands, but they are an ADDITIONAL line of defence.
[See part 2: DIY Masks]
Face coverings can be really useful in a population, to reduce the spread of the virus. Many people who think they are healthy and behave as if they are healthy but actually have Covid-19 and just don’t know it yet . Estimates average that around 40% of cases of infection come from people who thought they were well. So if only people with symptoms (who should have stayed home anyway) wear masks, the virus is still actively spreading through those who don’t know they have it – unless they wear a face covering.
NOTE – if you wear a mask with a valve (such as N95 and some cycling masks), it will protect you from the virus but you will still infect others if you are infected, because of the valve. It would be easier to breathe in but doesn’t protect anyone else from what you exhale and so doesn’t meet the intention of the Government recommendation.
Also NOTE that breathing through your nose is always better protection from viruses (see the Google search list below) because nose breathing produces Nitric Oxide, which is important for many aspects of health but specifically relevant is how it destroys viruses and improves oxygen uptake in the lungs.
What’s your purpose?
A good starting point, is – why do you want to get a mask/face covering? Have a think about what matters for you personally.
- Because I’ve been told I should
- Because I recognise its value in case I’m an asymptomatic carrier
- Because I fear getting the virus from someone else
I will refer to these levels of purpose in relation to the levels of protection.
Levels of protection
If you work in a clinical or caring situation, where you are likely to be exposed to a heavy viral load daily, then medical-grade PPE (and the rules applying to their use) is what you need and I am not trying to address those situations.
‘Viral load’ is an important concept, relating to how much of the Sars-Cov-2 virus you are likely to be exposed to, what degree of risk is there of enough exposure to trigger infection, in the circumstances you will be in. 
However, if you are in the general public and following the guidelines for keeping your distance and minimising exposure, and recognise you may have Covid but not know yet, a face covering which you make yourself is suitable. (And if/when you do develop symptoms or test positive, stay home.)
Anything is likely to be better than nothing, but from what I’ve learned I would focus on two criteria –
- Can you breathe easily enough (through your nose) without feeling you can’t get enough air. This is vital especially if you intend to wear it for any length of time, but may be hard with a mask of more than 2 layers
- Can you imagine your covering stopping a sneeze, or you could try blowing out a candle with it on (not a scientific test! There is the complaint that people vary in their amount of ‘puff’ but therefore so does a sneeze). A synthetic knit would be unlikely to pass this test
Many coverings are being made by very accomplished stitchers, with two layers of tight cotton cloth and a filter, and that seem to be trying to mimic an N95 (fitted and with maximum filtration), but without the valve. You may well find these very hot, and hard to breath in, though they may be ‘effective’ at filtering. This might be OK with you if you are a purpose 3 person and willing to put up with any discomfort to feel more safe, but if you put yourself at 1 or 2, you may give up altogether. Something is better than nothing.
At the other end of the scale, there are suggestions you could wear a scarf or buff. They visually cover your face, but can you imagine them stopping your sneeze? A woolen scarf, maybe – ish – a chiffon scarf, probably not! A synthetic knit buff, perhaps – folded double or triple maybe, but certainly not single. So an individual who chose ‘purpose 1’ might be happy with this, as it meets the letter of the recommendation though perhaps not the intention. It is not likely to protect you, nor anyone else.
The matter of filtering incoming particles is about protecting you. The fabric itself is the barrier that catches droplets from you and thus protects others.
A note about removing your face covering – official guidelines for medical masks are to only wear and remove a mask once (when it gets damp, perhaps 20 min), replacing with a new mask, and not touching the face part as you remove and dispose of it carefully. Coronavirus is viable on the surface of synthetic surgical masks *for 7 days*, and in a Covid ICU there is certain to be plenty of virus on the mask. Hence the very careful procedures for removing and disposing (or disinfecting) of used masks.
However, wearing a homemade cotton face covering, though filtering out fewer particles than a surgical mask, is no less effective after 3 hours of wearing than when you put it on. So although it filters out less in absolute terms than a surgical mask (while still protecting others) it can be much easier to wear longer term.
I came across a very good series of articles from an air filter manufacturer [3. 4. 5], who has been doing technical tests on different fabrics. My take-away thoughts from these articles, for the best balance between filtering and breathability, are: Use 100% cotton t-shirt fabric (double layer) or cotton sheet/pillow case, or light weight denim, or cotton tea towel (not terry cloth). Most patterns work best with 2 layers even if it isn’t much more effective, so a 2nd layer can be helpful. On average, DIY masks are roughly about 2/3rds as effective at filtering as a surgical mask.
By all means have a read of the articles mentioned at the end, and see where the fabric you have available comes in the overall scheme of things. I find the t-shirt fabric is especially comfortable to wear, and breathable enough so that even double thickness so my glasses don’t steam up.
Some styles have a pocket to insert a filter, such as a paper towel or coffee filter. Yes, this will improve filtration. But check for yourself if it makes breathing too difficult. Having a pocket at least makes the filter optional, but potentially requires more sewing. I am much less in favour of the sewn-in filtration layer (quilt batting, or non woven interfacing) that is popular in many of the patterns online.
You basically want a good fit, which avoids gaps around the edges. Many shapes are available, but whichever style you use, a wire across the bridge of your nose will massively improve the fit, and significantly reduce the amount of fogging you get on your lenses. If you don’t wear glasses and are not trying to maximise protection, the nose wire matters less.
I find a mask I can wear around my neck when I’m out, and put on my face when I’m in a busy environment, works well for me. When I slide it down again, I wash or sanitise my hands – just in case.
If I have been to a supermarket, I will put it in the wash when I get home, or on the dashboard of a car in the sun. But if I’ve had it with me walking into town, and only worn it for the 10 min I was in a shop, then I will probably just leave it in a warm dry spot when I get home, and not use it again for a couple days. The combination of heat and time deactivates the virus, if I’ve picked any up. 
I therefore prefer cords that go around the back of my head and neck rather than around my ears.You can technically have cords behind your head instead of behind your ears, for every style I’ve seen so far.
If you wear glasses, clean them with lens cleaner or detergent/shaving foam/soap to reduce fogging, and make sure you have a wire to fit it round your nose. But the better you can breathe, the less fogging you will have.
This is long enough. In the next article, I will put links to a few patterns I’ve found online, in case you don’t want to sift through dozens or hundreds! I’m not saying these are better than all the others, but I like how they are presented and explained. Options for those who sew, and those who don’t.
I’ve read far more than I’ve included here, but these seem to be the best sources to summarise what I’ve gleaned.
- The Risks – Know Them – Avoid Them (Dr Erin Bromage)
- You could be spreading the coronavirus without knowing (New Scientist)
- Can DIY masks catch viruses? (P Robertson, Smart Air Filters)
- What are the best materials for DIY face masks? (P Robertson, Smart Air Filters)
- Ultimate face masks material (P Robertson, Smart Air Filters)
- Disinfect your mask at home (Columbia University)
- How long can coronavirus survive outside the body? (UK Research & Innovation)
- How long the coronavirus lives on surfaces? (Business Insider)
- How long does coronavirus last on surfaces? (Science Alert)
- About nose-breathing (Patrick McKeown, TED Talk video)
- Nitric Oxide and effect on viruses and oxygen uptake (Google list of published papers and articles)