Ventilation systems in classrooms

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SARS-CoV- or COVID- has presented relatively low infection rates in children under years of age compared to the rest of the population. However, serious cases and child deaths from this disease have been reported, so we must pay attention to the potential for contagion in classrooms. Table of Contents Indoor air quality and the role in disease transmission Recommendations for the prevention of infections The WHO officially indicates mechanisms of contagion of COVID- : Direct contact, given by physical contact between an infected person and a susceptible host. Indirect contact, when a person comes into contact with an infected object or surface. By respiratory droplets, a situation that occurs when an infected person disperses droplets when speaking, sneezing and/or coughing and these reach a potential host. But there are new studies that show another mechanism of contagion: airborne or aerosol transmission . These are particles smaller than microns and are composed of a greater amount of organisms and dry material than water. Tuberculosis, Measles and Influenza are examples of pathogens that can be spread via airborne transmission. Indoor air quality and the role in disease transmission The United States Center for Disease Control and Prevention (CDC) points out that there are documented examples that indicate that the COVID- virus could have been transmitted over long distances and times (Scientific Brief: SARS-CoV- and Potential Airborne .

Transmission) , Scientific Review. October , ). These events occurred in places where there was the presence of one or more infected people emitting respiratory droplets for times greater than minutes or even hours, in closed spaces. Given situations and studies similar to this one, the WHO indicates that situations of contagion by aerosols in closed and crowded places, with poor or no ventilation systems, cannot be ruled out . One way to control air quality in classrooms is through CO sensors. A greater amount of CO in the air does not make viruses like Poland Email List COVID- stronger or weaker, but a high concentration of this is not an indicator of poor ventilation. International recommendations indicate that the CO concentration should not exceed ppm or about ppm above the base level of outdoor air. To achieve optimal ventilation levels, the Harvard Guide to Classroom Ventilation recommends at least renovations per hour for students per square meters. Another calculation that can be made and that is recommended in this same guide is to consider liters per second per person (double the ASHRAE standard). This would be like this: Renewal hour = liters per person and second * number of people * seconds/hour * m/liter / room volume in m It should not be forgotten that ventilation, controlling the volumes of CO and/or with the recommended flow rates and renewals, is as important as the design of the ventilation systems.



The air injection must be carried out preventing the air flow from directly impacting people. Filters must also be implemented to capture particulate matter coming from outside. As for the air intakes, they must be located in such a way as to avoid the existence of dead zones where the air is not renewed. Humidity and environmental temperature is another way to prevent the spread of diseases. The literature tells us that a relative humidity between % and % is the most unfavorable for the survival of microorganisms (“Academic Research to Support Facility Guidelines Institute & ANSI/ASHRAE/ASHE Standard ”. ASHRAE Research Project CO-RP Atlanta : ASHRAE). Humidities below this % are associated with factors that increase infections, because if this is accompanied by sufficiently high temperatures, the drying of larger respiratory droplets is facilitated, giving way to aerosols that remain for longer. time in the air. Both relative humidity and temperature are factors that can be controlled with sensors and ventilation systems. Recommendations for the prevention of infections Although the spread of COVID- through aerosols is still being studied, air distribution, filtration and ventilation systems have the potential to limit the transmission of various pathogens and, therefore, break the chain of infection. Keeping classrooms ventilated, ideally with forced ventilation systems, designing them efficiently, avoiding areas without air renewal, avoiding excessive hourly renewals that affect comfort and maintaining relative humidity, ambient temperature and CO concentration at optimal levels will help mitigate the effects. risks of contagion of various pathogens and greater safety in this area in the classrooms.