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Poor Ventilation Could Cause Super-spreader Events when Schools Reopen

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Broken AC unit causing poor ventilationAccording to the World Health Organization, one of the central transmission methods for the Covid-19 virus is through nose and mouth secretions that travel through the air as tiny droplets. However, the truth could be more insidious. These tiny droplets can stay suspended in the air for up to 16 hours. A recent preprint article by University of Nebraska Medical Center, which was published in medRxiv, has shown that the virus is likely airborne, which is not good news for schools reopening. With poor ventilation in schools, reopening our schools could lead to super-spreader events.

Crowded rooms with poor ventilation have created superspreading events before. Back on March 17, 2020, a two-and-a-half-hour choir practice in Skagit County reached national headlines. After just one practice that involved one symptomatic infected individual, 87% of the 61 member choir became ill with Covid-19.

The most likely culprit for such a superspreading event was the inhalation of respiratory aerosol droplets that had spread out to a uniform distribution over the room, a preprint paper submitted to medRxiv proposed. Additionally, the use of loud, singing voices certainly spread the droplets more, but poor ventilation kept the air recirculating within the room rather than creating enough air exchange with the outside. The researchers concluded through their simulation that doing high-emission activities such as singing for more than a half hour in indoor locations that follow current U.S. standards brought a higher than 10% infection risk. Enhanced ventilation and mechanical filtration could have mitigated the risk but not completely.

What happened with the Skagit Valley Choir does not bode well for schools. There are many similarities between a choir and a classroom. Classrooms are very active places with people speaking loudly, singing at times, and a lot of chatter. With the high probability of schools opening without proper social distancing, classrooms may be too crowded and kids may be in close proximity, just like in choir rehearsals.

For schools to reopen, the Centers for Disease Control and Prevention’s (CDC’s) guidelines have recommended proper ventilation and airflow. Furthermore, the CDC also recommends opening doors and windows. Ideally, there should be fans blowing to provide a rapid exchange of air, which will help to decrease the concentration of aerosol droplets in the air. Concentration matters with respect to the rates of infections. However, opening windows is not practical for most schools due to the cold, the heat, the weather, or allergens.

Poor ventilation in schools is problematic for safely reopening

Relying on school air conditioners and ventilation systems is problematic for a number of reasons. Many of our school districts haven’t repaired their ventilation systems in decades. This year, the U.S. Government Accountability Office found that an estimated 41% of Public School Districts need updates or replacements for their heating, ventilation, and air conditioning (HVAC) systems. Without money, schools won’t be able to fix the HVAC systems, and therein lies the problem.

It was hard for schools to find the money to fix the HVAC systems in the pre-COVID-19 years. With the budget shortfalls, we cannot expect schools to fix all the outdated systems in the next few months. Accordingly, poor ventilation issues are going to affect school reopenings.

Renovation itself may not be enough. Many schools that have renovated their HVAC systems have focused on energy savings rather than adequate ventilation. Subsequently, the results have been poor. In a study reported in the National Library of Medicine, the ventilation rates of 37 recently constructed, recently renovated, or mechanically ventilated U.S. schools were analyzed. Only 22% of classrooms met the recommended minimum ventilation rates. Consequently, renovations need to be focused on providing adequate ventilation rates rather than just energy saving. The statistics also came from 2017 before Covid-19 and refer to a comparison with ventilation standards at the time, not the enhanced standards that would take into account removing an airborne virus.

The increasing consensus that Covid-19 is airborne is quite new, which should change our perception of what is needed for schools. Even if the ventilation rates adhere to current standards, it will not mean the ventilation rates are good enough to remove the aerosolized droplets from the air, as was seen with the choir in Skagit County. Recirculation of air is not enough. Instead, airborne viruses could be blown around and spread more with an air conditioner or indoor fan. There must be a complete exchange of air.

The poor ventilation in schools has teachers very concerned

Stephanie Texler, a Michigan drama teacher, expressed her fears. “I have not met one teacher who is a fan of going in person in the fall. We are all very concerned about the health issues if we have to go face to face. One thing that I don’t think people realize is that the HVAC systems in schools are awful. The air in a room is stagnant or it is freezing cold. Half of the building is one way; half is the other. There is no good circulation. My husband’s school doesn’t have air conditioning. Can you imagine wearing a mask on the third floor in 95 degree heat? So the kids aren’t in masks and we don’t have good air filtration systems. It just seems very terrifying to all of us to go back even though we want to, we want to be with our students.”

Alison Stackpole, a speech language pathologist, who is teaching in North Carolina spoke to us with a similar message. “Schools are not a great setup. It’s all inside. There are lots of people inside. Then even within the building, you have got different classrooms where it is closed up. There are some schools where the windows don’t open. They physically cannot open the window. It’s not great circulation.”

CDC guidelines unfortunately come in the form of recommendations rather than requirements. Due to the challenge of implementing proper ventilation in classrooms and schools, many schools may decide to ignore ventilation issues and focus instead on the wearing of masks. However, masks do not eliminate the droplets leaving people’s mouths unless they are N95 masks, which are not yet required. Thus, in rooms with poor ventilation, the wearing of masks might not affect the infection risk at all. After some time, the aerosol droplets would distribute uniformly across the room.

Everybody wants our children to get back in school.  Remote learning is not of equal quality to face-to-face learning. Reopening schools is a priority, but it has to be done safely. Unfortunately, poor ventilation in schools makes it difficult to reopen safely, and worse, yet, the lack of adequate ventilation may increase superspreading events.

Read more on how Covid-19 is impacting schools with staff shortages, bus driver shortages, and social distancing difficulties.