When you say a sentence like “Dad, don’t speak louder!“, know that you project the exhaled air with possible postilions more than two meters away in a few seconds! It is indeed reveals a study carried out by researchers of the universities of Princeton in the United States and of Montpellier in France published in the Proceedings of the American Academy of Sciences.
From 50 centimeters to 2 meters depending on words and diction
Wondering about the possibility of transmitting the Covid-10 during a simple face-to-face conversation, the scientists wanted to know more precisely how far and in how long we project the plume of air expired while speaking. Through physical experiments (by visualizing airflows with a laser) and simulations, they established that if a person breathes or speaks normally, they project this plume in front of their mouth about fifty centimeters in a fraction second. But the distance goes up to 1 meter when the air is accelerated by the pronunciation of occlusive consonants such as p! Worse still: if several consonants follow one another in the same sentence, we can therefore reach 2 meters.
Viral particles are carried away by the exhaled air
“We knew that occlusive consonants favor the formation of postilions, but we now see that they also greatly accelerate their transport in the air in front of the mouth.“says Simon Mendez, one of the study’s authors. However, in a person infected with SARS-Cov2, the small respiratory droplets loaded with virus infecting the throat follow almost the same trajectory as the plume of exhaled air. Viral particles then travel in less than a second almost a meter distance in front of the mouth and up to two meters depending on the words spoken, even if they are then diluted in the ambient air.
The researchers also point out that virus concentrations could become much higher if the infected person speaks for a long time, loudly, or is in a confined space, which may be the case in a restaurant, a choir or the bleachers of a theater. sport competition. To reduce the risk of contamination in the current epidemic context, they therefore advise avoiding talking face to face for too long and within two meters of your interlocutor, which is already recommended in the United States, and of course to wear a mask.
by Pierre Kaldy