The video that demonstrates the danger of wearing a poorly fitting mask

The main symptom of the fight against the coronavirus is the mask, whose use has been shown to be one of the most effective measures to stop the transmission of the virus. But as long as it is used well. Misused is useless. The proof It is a video that has gone viral.

This idea is what the Spanish scientist has transmitted Jose Luis Jimenez, one of the world’s leading experts in aerosol transmission and a professor at the University of Colorado (United States).

In a thread posted on Twitter, Jiménez assures that “there is a lot of confusion” on the subject of masks. “I have consulted the experts and I summarize it here”, said the university professor.

“To understand the details, you must first understand how the virus is transmitted. Three ways, in order of importance: inhalation of aerosols, in close proximity, and sharing air in a room; spray droplets (projectiles) and touch contaminated surfaces “, explains the teacher.

“After touching the contaminated surfaces, we have to touch the inside the mouth, nose, or eyes (…), scientists think that it is unimportant. The masks help that we do not touch nose and mouth, “he continues.

“To (stop) the projectile drops, just a cloth hanging in front of the nose and mouth, and intercept those projectiles“, says the professor, who adds that” for the inhalation of aerosols, things are more complicated “.

“For aerosols, masks are a filter. The air we inhale and exhale must pass through the filter cloth. In doing so, many of the aerosols stick to the cloth. Quality and fit. The mask does not need to be well adjusted, or that is of very good quality“says Jiménez.

“The quality of the fabric for filtering means that the percentage of the aerosols that pass through remain stuck. It must be understood that filters are not strainers or sieves. Microscopic physics surprises. They can trap aerosols much smaller than their holes “, explains the professor.

“You also have to understand that the virus does not travel naked in the air. It comes out in particles of respiratory fluid and saliva, with mucin, sodium chloride, and so on. That are much bigger than the virus. And that is what has to be filtered, easier than if the virus were alone, “says Professor Jiménez.

Regarding the type of masks, “it is seen that N95 / FFP2 filter very well, the surgical ones also (but they fit much worse). The three-layer fabric, or two-layer ones with filter in the middle also filter well. “

According to Jiménez, the fabric masks that work best have “three layers of fine fabric, with the one in the middle different from those outside. Or a good filter between the two layers. “

“To filter aerosols, we need filter quality and mask fit to the face. Because if there are gaps between face and mask, the air is easier to go for them. A gap of 2% of the mask area allows 50% of the unfiltered air to pass through, “he explains.

“The fit is a very big problem for the use of masks for the general population. Half of the unfiltered air passes through gaps that seem small to us. In this video (from the University of Delft) you can see three masks, the N95 and surgical they are poorly adjusted and have a lot of leaks“.