Edgar landivar 
When the pandemic surprised the world, we did not know where to run, the doctors did not know what treatment was the right one for this unknown mutant, and citizens became paranoid, taking extreme care in everything. We self-imprison ourselves until everything goes back to the way it was before. The governments, without knowing what to do, came to wash the streets and sidewalks of some cities, with jets of water mixed with disinfectant. But time has passed and now the matter is much clearer.
We have learned what does not work and what does. At this point, in mid-2021, something is already evident: the coronavirus, as well as most of the viruses that affect the respiratory system, are transmitted through the air we breathe.
There are already several studies that suggest that indoor air quality it's key. In particular, there is one parameter that must be closely watched: the carbon dioxide or CO2.
CO2 and its relationship with viral load
What studies have found is a strong relationship between CO2 and viral load of a closed place. And it is logical, CO2 is the main waste product of human respiration.
At the end of March, a hundred Spanish scientists decided to send an urgent letter to their government, making recommendations on how to address the issue to minimize infections. Point 4 of these measures literally says the following:
The CO₂ measurement is the best, if not the only, low-cost technology solution available to check at all times if the ventilation is sufficient or if it is necessary to increase it. It also allows you to optimize ventilation, avoiding excessive air currents or unnecessary air conditioning consumption. In addition, it has a very low cost and constitutes a totally viable solution in any activity, public or private. For all these reasons, we consider its urgent and generalized implementation necessary.
https://elpais.com/ciencia/2021-03-25/es-urgente-abordar-de-forma-coordinada-la-transmision-de-covid-por-aerosoles.html
When excess CO2 doubles the risk of transmission, so does
In the month of April of this year, a group of researchers from the University of Colorado, in Boulder, reached this conclusion, about what happens when the excess of carbon dioxide.
Zhe Pen, one of the leading researchers in that study, says the following.
Monitoring CO2 is really the only practical, low-cost solution we have for monitoring. There is nothing else
https://www.sciencedaily.com/releases/2021/04/210407143809.htm
The studies kept coming, but authorities in some countries have been slow to react. However, countries that are at the forefront have already made important steps towards adopting carbon dioxide monitoring in schools and indoors.
Safe levels of carbon dioxide
Outdoors the CO2 level is generally around 400 ppm (parts per million). Indoors this value rises. However, existing regulations generally begin to set a safe limit between 1000 and 2000 ppm. Above that, it is considered that there are problems of ventilation or crowding of people.
The first initiatives
After the indisputable amount of scientific tests at the request of the CO2 monitoring, the first governments have begun to take action.
For example, the city of Buenos Aires has launched a massive initiative, giving away 33,000 CO2 monitors to schools, as part of a safe back-to-school campaign.
In Spain, several cities and especially institutions such as universities have adopted this measure for an upcoming return to classes.
- UNED case: https://www.eleconomista.es/ecoaula/noticias/10904296/11/20/La-UNED-instala-medidores-de-CO2-para-facilitar-la-asistencia-presencial-segura-frente-al-COVID19.html
- University of Valencia case: https://www.lavanguardia.com/vida/20210520/7469368/uv-instala-sistema-monitoreo-co2-prevenir-contagios.html
There are also initiatives in Canada, the United States, Australia and several European countries. If everything goes as expected, we will be back in an almost normal world, but very cautious, soon.
