From the onset of the pandemic, Richard Corsi, who has studied indoor air quality for decades and who has notably contributed in the past to the development of an environmental engineering program at the University of Guelph, is given the challenge of finding practical solutions to stem the spread of the virus.
This dean of Davis College of Engineering from the University of California knew that the virus can be transmitted by aerosols and droplets and therefore it is possible to reduce the risk of transmission by purifying the air.
I was wondering how to build something that would be cheaper [qu’un purificateur d’air HEPA]while reducing the amount of virus particles people breathe in.
In the end, the solution was deceptively simple, he says.
Mr. Corsi was inspired by people who install a filter on a fan in an attempt to reduce the amount of harmful particles during forest fires.
I figured if we could pass a lot of air through multiple MERV 13 filters, we could remove a lot of particles from the air.
He knew that this basic model had to be improved and adapted for long-term use. He shared his idea on social media and quickly got help from Jim Rosenthal, the CEO of a filter company in Texas.
The box was also named in honor of the two engineers.
It is composed of four MERV13 filters and a square fan of the same size as the filters, assembled using adhesive tape. The air enters the box through the filters on the sides, sucked in by the fan, the propeller of which must be turned towards the air outlet, on the top of the box.
At the suggestion of a user, they added a cardboard fan deflector over the fan to prevent too much air resistance, which would have weakened the motor.
Mr. Corsi suggests replacing the air filters every 6 months.
The box’s effectiveness was tested by researchers at the University of California, affiliated with the Western Cooling Efficiency Center of Davis, and the results were published in the journal Aerosol Science and Technology (New window).
The box has proven to be incredibly effectivesays Richard Corsi.
Tests have shown that they are more effective than much more expensive HEPA air purifiers.
For example, experts typically recommend five to six air changes per hour in shared spaces, which means a room’s entire volume of air is replaced every 45 minutes. A Corsi-Rosenthal box manages to make seven or eight air changes per hour.
It is enormous. Most mechanical ventilation systems in buildings cannot change the air as oftensays Mr. Corsi.
While it is not possible to say exactly how many SARS-CoV-2 particles are filtered by a box, Mr. Corsi recalls that these types of filters are already known to eliminate pollen particles, mold spores and other polluting particles.
Even if we weren’t talking about COVID-19, that would be a good idea.
He adds that using the Corsi-Rosenthal box is much less energy intensive than some mechanical ventilation systems.
One more tool in the arsenal
Despite the effectiveness of the box, Mr. Corsi believes that wearing a mask remains the most effective way to reduce the spread of COVID-19. But he recognizes that this measure is now politicized and that other means of protecting people must be found.
” Without a mask, another way to reduce the amount of virus you breathe in is to improve ventilation and air filtration. »
According to Mr. Corsi, the Corsi-Rosenthal box is an additional tool in the fight against this virus and is even more relevant since the withdrawal of all sanitary measures.
This is why he is surprised when he hears that certain authorities, including the Quebec government, are reluctant to use air purifiers. In fact, in February, public health told The Press (New window) that
an air purifier does not add value when there is adequate ventilation in a classroom. Yesterday, the Minister of Education indicated that he favors natural ventilation, that is, opening the windows, even in winter.
Jim Rosenthal had also criticized the Quebec government on this subject:
Excuse me, but the Quebec government’s decision not to buy HEPA air purifiers is stupid. It’s based on the ridiculous idea that HEPA filters increase the risk [de transmission]. What? he wrote on Twitter in April 2021 (New window).
According to Mr. Corsi,
the biggest risk associated with using it is someone tripping over the box!.
The government of Quebec partly changed its position and, since then, the Ministry of Education has distributed just over 1,500 air exchangers, at a cost of nearly $13 million. By comparison, at $100 each, 1,500 Corsi-Rosenthal boxes would have cost $150,000.
Already a few boxes in Quebec schools
For nearly two years, Corsi-Rosenthal boxes have been used in training centers, schools, restaurants, hospitals, offices in the United States, India, Europe, New Zealand. Schools and even groups like the scouts organized big chores to build several boxes.
Mr. Corsi uses one of these boxes at home when he has visitors and has had boxes installed in most classrooms at the university where he is now dean.
Moment of zen
6 months of operation at approx 60 hrs per week in the dean’s suite@UCDavisCOE. Dozens and dozens more across college, lowering inhalation dose of respiratory and other aerosol particles. Just do it, folks! pic.twitter.com/W7awZIPedF
— Richard Corsi, PhD, PE (Texas) (@CorsIAQ) July 31, 2022
In Quebec, a few people have chosen to go against the grain and install these boxes.
Lyne, a mother and volunteer in a primary school library in Mauricie, obtained the agreement of the teacher with whom she shared a room.
I knew that the Corsi-Rosenthal box was going to give us a plus, and that was enough to use it. A [filtre] Working HEPA is better than no HEPA at all, no offense to public healthsays this mother who does not want the name of the school to be disclosed, for fear that she will be prohibited from using the box.
For less than $50, she found all the parts needed to build the box.
At that price, there was no question that I do without.
Since November 2021, a Corsi-Rosenthal gearbox has been operating at low speed every school day, from 7:30 a.m. to 3 p.m. The mother explained to the students how the box works and is useful.
It is the students who start the machine every morning. They were very respectful and never tried to touch her.
On days when the kids couldn’t go out because of the weather, the fan speed was increased, even though it was noisier.
Generally, the box reaches between 58 and 67 decibels. A fridge emits an average of 50 decibels.
If this mother says she cannot scientifically measure the impact of the box, this class has not experienced an outbreak. In addition, she noticed that the local has much less dust and allergens with the box.
” Did it affect the contamination? Maybe. I dare to hope so. I believe it. »
Lyne says he
is amazing and shameful that this simple solution is shunned in Quebec.
In Gatineau, the principal of Pierre Elliott Trudeau elementary school has chosen to install a Corsi-Rosenthal box in each of his 28 classes. The school has also obtained a grant from the Quebec government for this innovative activity.
David McFall says the government’s addition of CO2 sensors to classrooms has been much appreciated. On the other hand, he was looking for other ways to reduce the risk of transmission, while offering an educational activity to his students.
” There is no magic solution. But every action adds up and allows us to have a safe environment for children and staff. »
Over a period of seven days, the fifth and sixth graders built enough Corsi-Rosenthal boxes for the whole school. The young people then explained to the other students how the device worked.
Mr. McFall adds that these boxes are no louder than a conventional fan.
This year, classes will once again use Corsi-Rosenthal boxes; the school will only have to change the filters.
An opportunity to educate
Richard Corsi is happy to see that these boxes have generated so much enthusiasm, but, as an educator, he is even more delighted to see that they have led to awareness of the importance of the quality of the ‘air.
It’s a way of teaching children that you can be a citizen-engineer, that you can build something beneficial. Children learned about airflow, particles, aerosols. When they plug in the box, they have a sense of accomplishment.
David McFall agrees.
Students are very aware of the risks associated with COVID-19. The boxes gave them the chance to be part of the solution. He hopes other schools will make their own boxes to deal with possible fall or winter waves of COVID-19.