As a football fan, the masks you knew were the ones that players wore when they had to protect their skulls or noses. In 2016, there were so many Chelsea players wearing masks — Cahill, Azpilicueta, Matic and Costa — that their coach, Guus Hiddink, before playing a game against Newcastle, said they looked like the “El Zorro” team.

The masks worn by footballers are made with exquisite technology. The player’s face is scanned and the mask is 3D printed, with a material called UTEM9085, a fibre that is also used in the aviation industry.

To combat COVID-19, we need a large production of masks. But what kind of masks do we need?

Masks could be classified into two main classes: (i) those that mainly cover what comes out (what you breathe out), and (ii) those that also protect you very well from what goes in (what you inhale). I bring you good news: all the masks, to a greater or lesser extent, help to prevent the virus from spreading along with the risk of you becoming infected.

Within the first class are surgical masks, those blue or green ones that doctors wear so as not to infect patients while operating, blocking microbes that could come out of the mouth or nose. The masks that you can make at home with any fabric could also serve, more or less effectively, for this mission. This class of masks are suitable for routine use by the general population. In football terms, they serve to try to avoid anyone scoring.

The second type of mask is respiratory, which also filters the air you breathe from outside. These are ideal so that you don’t catch a virus; so that you don’t concede a goal. Therefore, they are suitable for healthcare personnel in contact with COVID-19 patients. Within this category there are several subtypes according to their ability to filter particles. Let’s say that an FFP3 is to have Oblak as a goalkeeper defending the goal of your mouth. Then there are FFP2 and FFP1, with a worse filtration efficiency. If an FFP3 is Oblak, an FFP2 could be Keylor Navas, a very good goalkeeper, but who is clearly no Oblak.

FFP3 and FPP2 are European standards, which correspond to the American N99 and N95, respectively. All these masks can shield you, even from a point-blank sneeze. Underneath these categories of regulated masks, a makeshift homemade mask could offer you the level of protection of Luis Ricardo Guevara Mora, who was the goalkeeper of El Salvador in the World Cup in 1982. Poor Guevara let in 10 goals against Hungary on his World Cup debut. Guevera’s embarrassment could have been reduced by subbing him with the reserve goalkeeper. But when they sent the latter to warm up with El Salvador losing 6-0, he refused; saying taking part in a World Cup was overrated.

 In a scientific article from 2008, the ability of different types of masks to protect you from what you inhale and protect the rest of what you exhale was methodically studied 8. This article concludes that N95 (or FPP2) masks or higher are much better for filtering what enters you, but that, when it comes to containing what you breathe out, the different types of masks are more even. It happens that in this investigation they used particles with diameters from 0.02 to 1 micrometre —one-thousandth of a millimetre—, and we know that the SARS-CoV-2 is around 0.1 micrometres in diameter. Therefore, particles smaller than coronaviruses were used in the study. In other words, these scientists shot some penalties with tennis or golf balls towards the masks and, of course, they scored more goals than normal. 

Recently, a group of Chinese scientists corrected the ball-size problem using a virus of the same shape and size as SARS-CoV-2 to study its ability to cross different types of masks 9. In this publication, Jan Oblak, as expected, had an extraordinary performance. FPP3 Oblak cut 99.98% of the micrometre balloons. The good news is that the surgical mask caught 97.14% of the spherical viruses. The performance of the surgical mask was much better than expected. It was something like selecting Iker Casillas as a goalkeeper, and he played a great game despite his recent retirement. So, all in all, a pleasant surprise, but not so strange either.

Undoubtedly, the great surprise of this research work was the Guevara homemade mask, which silenced its critics by stopping 95.15% of the microballs. Of course, in this experiment a reinforced guevara was used, with a piece of cloth and up to four layers of kitchen paper. Scientists note that the kitchen paper between the cloth and the mouth is a very good option, since the kitchen paper can be renewed every time you use it.

In short, it turns out that a homemade face mask, in terms of stopping a shot on goal (a sneeze), is so much better than leaving the goal empty, and it can stop more viruses than you might imagine if they don’t shoot at you from too close or constantly.