Last month we were told that only healthcare workers or people caring for loved ones with COVID-19 at home need to wear a face mask. But this week the US Centres for Disease Control and Prevention (CDC) advised: “Everyone should wear a cloth face cover when they have to go out in public.” Germany’s Robert Koch Institute and the German National Academy of Sciences have both issued statements supporting the wearing of masks in public. Spain and Italy recommend the use of face masks on public transport and other areas where close contacts are likely.  Speaking to the BBC Dr David Nabarro, a British official at the World Health Organisation said it would be “a good thing” if the public wore “some form of facial protection.”

The thinking behind this advice is that experts now know that people can transmit COVID-19 even when they’re asymptomatic (they have the virus but don't show any symptoms) or pre-symptomatic (they're carrying the virus and will eventually have symptoms). As many as 25% of people with COVID-19 may stay asymptomatic, potentially spreading the virus without knowing it, and those who are pre-symptomatic may be even more contagious, transmitting the virus for up to 48 hours before they have symptoms.

Because surgical masks and N95 respirator masks needed by health workers are in short supply the recommendation is that you make your own or purchase homemade face masks sewn by someone else.  It’s suggested that you wear a face covering whenever it may be difficult to maintain the social distancing rules such as when on public transport or while shopping.

Protecting Others

Since COVID-19 is transmitted through respiratory droplets expelled into the air from coughing, sneezing or close conversation,  the whole point about wearing a homemade face mask is to protect other people from what you might be spreading. A sneeze can potentially travel up to almost 8 metres (26 feet), and with the arrival of the peak hayfever season, more of us will be sneezing more often. If you’re an asymptomatic COVID carrier, your sudden sneeze could unwittingly make you a long-distance super-spreader. Wearing a mask would help to contain that.

Protecting Yourself

Although it’s not their prime purpose, homemade face masks may provide some protection for the wearer too. They may help to protect you from getting the virus directly into your nose and mouth if somebody coughs or sneezes right by your face. Similarly, just as wearing wraparound glasses helps to prevent the virus entering through your eyes acts as a barrier to stop you touching them so often, so can a mask keep you from touching your mouth and nose, the primary way the virus is spread.

According to Dr. Steven Q. Simpson, M.D., professor of pulmonary and critical care medicine at the University of Kansas in Kansas City, if you’re looking after someone in your household with COVID-19, having the sick person wear a mask while you wear one, too, will likely help protect you from getting the virus.

Best Material for a Homemade Mask

In a 2013 study published by Cambridge University Press in Disaster Medicine and Public Health Preparedness, researchers examined masks homemade from several household materials as an alternative to commercial face masks. They concluded that a homemade mask should only be considered as a last resort to prevent droplet transmission from infected individuals, but it would be better than no protection.

Using a highly concentrated aerosolised virus in 0.02-micron particles - smaller than COVID-19 – the researchers tested material from

• a tea towel
• a 100% cotton t-shirt
• a cotton blend t-shirt
• a pillowcase
• a HEPA (High Efficiency Particulate Air) vacuum cleaner bag
• a scarf
• some silk
• some linen

The surgical mask material used as a comparison blocked the most particles (89%), followed by the HEPA vacuum cleaner bag (86%), tea towel (72%), cotton blend t-shirt (70%), antimicrobial pillowcase (69%), and linen (62%). However, in terms of breathability and comfort, the 100% cotton T-shirt came out best, its stretchiness also giving a better fit.

Inserting a piece cut from a HEPA vacuum bag into the folds of a T-shirt face mask would therefore seem to offer the optimum DIY solution.

You will have seen a variety of instructions on the internet for homemade face masks, some using a sewing machine, others suggesting an origami style fold-and-staple option.