Ventilation in classrooms:Summary of the CSIC recommendations guide

Controlling safety in classrooms against the risk of virus transmission is one of the main concerns currently found in the population. The use of masks, hygiene, but we can control the air our children breathes?

A guide from the Institute for Environmental Diagnosis and Water Studies (CSIC) us teaches how we should ventilate classrooms correctly to reduce the risk of spreading the virus in addition to the recommended tools to measure if we have done it correctly.


The importance of ventilation in educational centers in times of Covid-19

Following the publication of researchers from the University of California on the evidence in the transmission of Covid-19 through the air, Governments and institutions are already debating the possible implementation of security measures in public places such as work centers, shops and schools.

Regarding the consequences of exposure to a closed place with high concentrations of CO2, such as a classroom with a group of students, headaches, dizziness, aggravate respiratory problems, lethargy, difficulty in attention and concentration of the student, among others, may arise.


How to solve the risk of contagion in the classroom

In addition to promoting attention and school performance, to enjoy clean air in classrooms, the emission of CO2 in the air can be reduced with measures such as:

  • Decrease in the total number of people per classroom.
  • Promote silence or a low speech volume , since when speaking loudly, the CO2 emission multiplies.
  • Indoors, a more relaxed physical activity, since with increasing physical effort, more CO2 is emitted.
  • Good use of masks (well fitted).


In short, for reduce the risk of the virus spreading , the guide to ventilation in schools published by the CSIC recommends:

  • Use of a well-fitting mask, even when other people have just left the room. Check here how to protect the little ones in nurseries.
  • Reduction of the exposure time as far as possible, carrying out activities in outdoors and outdoors .
  • Increased interpersonal distance.
  • Ventilation or air purification, to eliminate or reduce the concentration of viruses in the air.


As we can see, in addition to the already known measures such as hand washing, the use of masks or social distance, after showing the latent risk of contagion through the air , is added that of ventilating and renewing the indoor air to minimize the risk of contagion in the classrooms.

And not only ventilate, but check if we have done it correctly and the air is free of viruses.



What is classroom ventilation?

Ventilation is the renovating the air inside a classroom using an automated or manual system (opening windows and doors) that allows the potentially contaminated indoor air to be replaced with outdoor air, considered clean and virus-free.


How to properly ventilate classrooms

To properly ventilate a classroom or room, the frequency and time in minutes of this action will depend on:

  • The square meters of the classroom or room;
  • The age and number of students and occupants;
  • The activity carried out in it;
  • The incidence of cases of the virus in the region where it is found;
  • The probability of the risk of contagion.

For example, for a classroom of about 100 m², with about 25 students between the ages of 5 and 8, the Harvard guide recommends between 5 and 6 air changes per hour.

In thisfree guide we detail how we should ventilate the classrooms correctly:


How we can check that a classroom or room has been ventilated correctly?

To determine that classroom ventilation is virus-free, the CSIC guide proposes methods and tools in order to quantitatively determine the ventilation of a classroom and be able to act.

It includes the carbon dioxide (CO2) level measurement indoors, it is used as an indirect measure of ventilation.

Generally outdoors, CO2 concentrations are usually between 400 and 420 ppm (Parts per million) approximately.

In an occupied building, indoor CO2 concentrations are raised by the CO2 exhaled by its occupants, which can exceed 1000 ppm.


Check air quality in classrooms with a CO2 sensor



To carry out this quantitative measurement of CO2 levels, experts recommend the implementation of a CO2 meter in each classroom to warn each time carbon dioxide levels exceed levels considered pollutants.

In this way, we can ventilate and renew the indoor air by opening the windows and doors for 5-10 minutes.

In addition, this guide details the characteristics that they consider desirable in a CO2 meter, which are:

  • Ability to provide downloadable raw data in .txt, .xls, .csv or similar file.
  • Temporal resolution of at least one data per minute.
  • Screen showing CO2 levels in real time.
  • Use of NDIR technology.
  • Cost between 100 and 300..


In the market, you can find CO2 meters that meet these requirements as theinnovative Air Guardian CO2 sensor, which changes color like a traffic light according to the health of the air. This, together with its easy transport and installation, makes its use quite simple in order to be manageable for everyone.

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