The restart of face-to-face classesalthough it is good news from an educational point of view, it raises the dilemma of how to avoid contagion, especially when there is no separation by time slots or distance between students, especially in the rainy season or in classrooms that incorporate air conditioners.
Doctor in Environmental Sciences Paola Almeidaprofessor at the Faculty of Natural Sciences and Mathematics at Espol, and researcher at the University of Colorado peter mckinney They work precisely on issues of air quality. They answer some of The Magazine’s questions about getting students to breathe clean air during indoor classes.
What methods of measuring air quality are recommended for classrooms?
It is recommended to install air quality monitors (one per classroom) that contain at least sensors for the measurement of particulate matter (PM2.5) and carbon dioxide (CO₂) included. Where possible, it should be preferred that the CO₂ sensor be infrarednon-dispersive (NDIR).
Because viruses are a form of particulate matter, it is important to have a particulate sensor for air quality measurement to detect the possible presence of viral load in the air.
Good ventilation is essential for the dispersion (decrease) of particles and, therefore, of viruses in the air. During our breathing process we exhale CO₂ into the environment and these emissions can contain a viral load.
By measuring CO₂ levels you can tell how good or bad the ventilation is in a place. High levels of CO₂ in a closed space indicate poor ventilation (accumulation of virus-particles) and a greater risk of being exposed to air contaminated with particles (viruses) that we will continue to breathe while we are in a closed place with little ventilation. Poor ventilation prevents proper air exchange that helps lower CO₂ concentrations.
Measurement of particulate matter and CO₂ levels are essential for determining air quality, especially when it comes to respiratory disease transmission.
Almeida and McKinney mention some reasonable sensor providers for these parameters (particles and CO₂) here: Awair, Kaiterra, IQAir, Wicked Device and SGS Galson.
As a reference, they mention that SGS Galson-type monitors were installed in public schools in Boston (United States), with the aim of monitoring air quality in classrooms as a mechanism to prevent the transmission of respiratory viruses, such as SARS-CoV-2.
It is important that air quality monitors are placed in places where they cannot be disturbed or suffer any interference. For this reason, wall monitors are recommended if possible. It is also important to have a monitoring platform (on the web) for all sensors. Most or all of the companies listed above have this feature, the researchers say.
What would be the requirements to guarantee good ventilation in the classrooms?
If the building or school has a central air conditioner (forced air) that supplies several rooms (classrooms), you have to make sure that is operating at the highest possible flow rates, with the maximum amount of outside air possible. This is the first assertion of Almeida and McKinney.
Additionally, it would be beneficial to install filters with at least MERV 13 (ASHRAE 52.2 standard) or F7 (EN779 standard) efficiency.
In facilities or classrooms that have units mini-splitit is recommended to open any existing fresh air intake and install the highest level air filter possible on these air conditioners.
“Do not assume that the air filter in a mini-split does something to improve the air quality in the room, unless the filter inside it is specifically a MERV 13 or higher level. Otherwise, it will only recirculate the particles in the room, increasing the risk of contagion in the occupants of the classroom”, the academics insist.
It is important to note that although some of the mini splits have fresh air/ventilation options, this will almost certainly not be enough for a classroom full of students.
Almeida and McKinney have other suggestions for additional ventilation. “For rooms that do not have central air conditioning the following is recommended”:
- leave so many open windows and doors as possible.
- At a minimum, let a door and a window or two open windows on opposite sides of the room.
- If possible, place a ventilator to extract the air of a window or door.
What other equipment could help improve the air in the classroom?
The use of portable air purifiers helps, when they have the following characteristics:
- They must have one clean air delivery rate (CADR) suitable for the size of the room. The technical definition of CADR is the amount of clean air, free of contaminants, delivered by the device. This is expressed in cubic feet per minute (cfm).
- Two or more small air purifiers are often better than one large air purifier which gives the same total CADR.
- they must be able operate quietly so teachers leave them on.
Carrier air purifiers, for example, were successfully used in public schools in the city of Denver in the United States, with the purpose of providing and improving air quality in classrooms.
A fan in a window or door, if outside air quality and temperature conditions allow, would provide better ventilation, the researchers insist. “Finally, if there is a central HVAC (heating, ventilation, and air conditioning) system, upgrade air filters to MERV 13/F7, minimum.
Preparing for an uncertain future in the field of viral respiratory diseases
The study and identification of viral diseases transmitted by the respiratory tract is a broad and highly complex topic, according to Paola Almeida and Peter McKinney. A significant increase in viral diseases (respiratory type) is estimated in the near future. “It is necessary to have prevention mechanisms to, as far as possible, counteract the risks caused by this type of disease.”
The monitoring of air quality inside closed places, such as classrooms, It is essential for the prevention of massive infections. “This will require a significant investment by educational and government entities that seek to counteract and minimize the risks of contagion in educational centers.” (I)
Source: Eluniverso
Paul is a talented author and journalist with a passion for entertainment and general news. He currently works as a writer at the 247 News Agency, where he has established herself as a respected voice in the industry.
