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Schools implement extra layer of safety with improved ventilation

October 23, 2020

At the start of the pandemic, no one thought we would be out of school for more than a few weeks, let alone seven months. Some were even optimistic during the middle of the summer when plans to return to hybrid were announced.

But as September approached, it was clear that the transition to hybrid would be delayed. One of the main factors of the delay was the safety of being in the school building itself. After extensive research and planning on the part of district leaders, the issue of ventilation has been addressed and the town is planning to reopen Old Lincoln School on Oct. 26 and 115 Greenough on Nov. 9.

In August, Expert Advisory Panel 4: Public Health, Safety and Operations met with Joe Allen, the director of Harvard’s Healthy Buildings Program. They discussed ways to reduce risk of COVID-19 transmission using ventilation and filtration and with his team’s recommendations, the school district is aiming for at least four air changes per hour in each room. David Gacioch, co-chair of the panel, said this will add an extra layer of protection against COVID-19.

Allen’s team has written a 60 page report describing a holistic risk reduction approach to keep students and adults safe in schools, as well as a five step guide to assessing ventilation.

After presenting the report to Expert Advisory Panel 4, Allen’s team demonstrated how to calculate air changes per hour using a method with dry ice and a tool called a balometer, which records air flow through a certain vent or grille. Air changes, which ensure airborne particles do not linger in a room for long periods of time, are an important safety measure for the return to in-person learning.

“A typical home gets .5 air changes per hour. That means it takes two hours for the air inside to be exchanged with outdoor air. So when you talk about six air changes per hour, that means the air is getting exchanged every ten minutes,” Allen said.

Before ventilation work started, Allen said many rooms in the high school had one to three air changes per hour. In order to bring that number up, portable air cleaners, open windows and open doors can and should be used.

“The idea is if you are hitting four to six air changes per hour, it doesn’t matter which method you are using. They are all interchangeable,” Allen said.

But particularly during the winter, the concern is that most windows will be closed. Gacioch said the school has already accounted for this.

“The way that the district is approaching this is to treat windows as a bonus, not as part of the baseline calculations to every room. The number of air changes per hour is going to be brought up to the enhanced target through a combination of mechanical systems and portable air cleaners,” Gacioch said.

According to Allen, filtration becomes even important during the winter when there is less airflow, as the windows will be closed.

“If someone is sick in the room and admitting infectious virus particles, we want to have masks on because that reduces the amount of viral particles that enter the air first,” Allen said. “These viral particles will stay in the air until one of two things happen, they are diluted out of the air through ventilation or they are cleaned out of the air through filtration.”

According to Matt Gillis, the Director of Operations for the School Business Service, the district has bought High-efficiency Particulate Arresting (HEPA) filters and other air filters to combat the issue of decreased ventilation during the winter. All of them have a Minimum Efficiency Reporting Value (MERV) rating of 13 or higher, which Gillis said meets the standard for capturing particles the size of the virus.

With this stronger filtration system, ventilation from outdoors is not necessary. As long as recirculated air is going through these filters, it can count as clean air, Allen explained.

“If you put in a better filter, then that recirculated air should also count as your clean air because the filter will capture the viral particles,” Allen said. “The way I think about this prioritization is that you want to bring in as much air as possible. On the recirculated air, you want to enhance the level of filtration. And then you want to supplement that with the use of portable air cleaners also using HEPA filters.”

Gillis said the district plans to buy a total of 1,050 portable HEPA filters using a portion of the 1.7 million dollar grant from the state. Not all the rooms across the district have been tested and gotten units deployed, but with a team of over 30 working on ventilation, including school staff and parent volunteers, Gillis estimates each room should be safe by Nov. 9.

However, Brookline School Committee chair Suzanne Federspiel has said that if a room is not at more than four air changes per hour by the time the high school plans to transition to hybrid, that room will not be used.

Recent issues have caused the hybrid start date for 1st-2nd graders and 9th graders to be pushed back from Oct. 20 to Oct. 26, with strong voices advocating for both sides. The administration has stated its hopes to return to in-person learning as soon as it is safe, but according to Gacioch, the cost of the ventilation improvements has not increased pressure to do so earlier rather than later.

“I believe our goal since the spring has been to give as many students as possible the chance to be back to in-person but only as long as in-person school can be done in a low-risk way,” Gacioch said. “The ventilation improvements have been part of the effort to serve that goal, not vice-versa.”

But ventilation and filtration are not the only factors in reducing risk of transmission. This is where Allen’s holistic risk reduction approach comes into play.

“Wearing masks is still one of the best and top priorities,” Gillis said. “Frequent hand washing and hand sanitizing is another one. Six-feet of social distancing is another one. Air quality and air cleaning is another. If any one of the layers flips for a moment, all the others are still backing it up. Each one is a layer of defense.”

Gacioch added that the ventilation goal of four to five air changes per hour must be seen as an added safety precaution on top of and supplementing these other measures.

“This is not just a matter of getting buildings up to a minimum safe standard or minimum code standard,” Gacioch said. “This is a real, extra step that is going to provide an extra layer of protection to everyone and it should, along with masks and distancing, help keep the risk of COVID-19 transmission in our schools as low as we can make it.”

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