This fall, teachers and parents shared photos on social media of DIY air purifiers they made for classrooms to help protect children from the transmission of COVID-19.
But do these low-cost purifiers really work?
According to the researchers, they do.
They’re called Corsi-Rosenthal Boxes, and they’re an air purifier first designed in the summer of 2020 by two air purification experts, Richard Corsi and Jim Rosenthal.
Since then, its effectiveness has been supported by scientists, studies and the company that manufactures air filters.
Studies have shown that poor ventilation is associated with a much higher prevalence of COVID-19. But many buildings in Canada, including schools and workplaces, are still not equipped with proper ventilation systems or HEPA purifiers.
Unlike HEPA scrubbers, which can cost anywhere from $200 to upwards of $500, the Corsi-Rosenthal box can be made for about $100 with materials that can be purchased at any hardware store.
The York University engineering professor, who carried his Corsi-Rosenthal box with him across campus last week, said he heard about them on social media in mid-2021.
“Some ventilation engineers were talking about them and it seemed like a practical and easy way to get more clean air in schools and in my home,” James Andrew Smith told CTVNews.ca in an email.
“I don’t think we’re doing enough for clean air,” he added, saying he feels better about the level of risk in his classroom when he uses his homemade air purifier along with other measures.
The boxes seem to be long-lived, too.
“This guy behind me just turned eight a few days ago,” said Corsi. In a Twitter video on Monday, pointing at his Corsi-Rosenthal box as he crossed his shoulder. “It’s still doing its job, it’s still doing the reduction of aerosol particles by inhalation, including virus-laden respiratory aerosol particles. It’s not rocket science, folks.”
What are Corse-Rosenthal boxes?
There are differences, but the basic Corsi-Rosenthal Box is made with four air filters, one box fan and some cardboard, all taped together to make a cube. a University of California, Davis Tutorial Specifies to use MERV-13 filters.
The air flow in the box fan should be facing outward, and all edges should be sealed with masking tape. The last sixth side of the cube should be sealed with cardboard or even a fifth air filter.
To make the filter more efficient, you can also cut a circle out of a piece of cardboard and stick it over the outside of the box fan to reduce backflow.
The idea behind the Corsi-Rosenthal configuration is that the air entering the box will pass through multiple purification filters, and the airtight cube means that only the filtered air will then be blown into the room by the fan.
Studies show that while it won’t be able to filter out as many particulates as a HEPA filter, the Corsi-Rosenthal Box can circulate the air in a room at a rate that sometimes exceeds HEPA purifiers, removing viral particles from the air. At a fraction of the cost.
study Posted in March In the journal Aerosol Science and Technology, which featured Corsi as one of its authors, it found that the boxes were able to quickly filter an entire room at a rate much faster than HEPA scrubbers.
When looking at the “cost per unit of clean air,” the study said, “a DIY air filter is roughly one-tenth the initial cost of commercially available HEPA-based air cleaners.”
3M, a company that makes air filters, said in a February press release That their scientists have studied Corse-Rosenthal boxes and that the DIY idea works.
“Indoor air is shared air,” Kelsey Hay, 3M Filtrete Brand Engineer, said in the statement. Many viruses such as COVID-19 are airborne and can be highly concentrated in poorly ventilated areas. I am happy to see so many people championing the importance of clean air, especially in schools.”
Another study Published in September in Science of the Total Environment looked at nine different DIY air purifier configurations and compared them to three HEPA purifiers.
The study found that DIY options, including one filter with box fan, Corsi-Rosenthal boxes, and a variation on them that uses three filters and two box fans in a cube, were all comparable to or better than HEPA purifiers in terms of how quickly the air was purified.
Clean air switch for lower cover transfer
When it became clear that COVID-19 had spread through air transmission, scientists began to stress the importance of good ventilation as a tool to slow transmission.
An Italian study published last March that looked at more than 10,000 classrooms found that effective ventilation systems were able to reduce COVID-19 transmission in schools by more than 80 percent.
Infection was significantly lower in 316 classrooms that were equipped with a mechanical ventilation system, compared to those without. When the ventilation systems were rotated to replace the entire classroom air with fresh air 2.4 times per hour, infection was reduced by 40 percent. The study found that if they replaced the air six times an hour, infection was reduced by 82 percent.
With few public health measures still in place to get back to school, teachers are increasingly turning to tools like the Corsi Rosenthal Fund to make their classrooms safer.
take class room
As students return to the classroom this fall, teachers and parents have taken to social media to share photos of Corse-Rosenthal boxes. On Twitter, the hashtag #CorsiRosenthalBox includes several creative designs that are meant to be kid-friendly.
One Manitoba-based user posted a photo of his son’s Corsi-Rosenthal Box class that had been upgraded to look like a robot with googly eyes, antennas, and arms.
Other designs have used large eyes, brightly colored paint, and a variety of animal ears to turn chests into friendly creatures.
In Quebec, parents and teachers I sent a petition Jean-Francois Roberge, Minister of Education, called for them to be allowed to provide Corse-Rosenthal funds to their children’s schools, saying citizens’ initiatives “met with strong administrative resistance”.
The description reads, “Installing homemade air purifiers, known as Corsi-Rosenthal cubes, is an effective and inexpensive way to improve indoor air quality.”
The petition, which began last month, has more than 1,600 signatures.
At the Lasound School of Engineering in York, Smith says navigating the Corsi Rosenthal box cart sparked questions and students’ curiosity.
“How much do I care about my students? Enough to build a #CorsiRosenthalBox with wheels to bring them to class,” He tweeted on Monday.
Smith and other faculty have called for the Dean’s Office of the Lasound School of Engineering in York to fund and distribute portable air purifiers to faculty, but so far, these suggestions have been rejected.
“Personally, I think they need no brainer,” Smith told CTVNews.ca. “They are easy to install and operate, and are not nearly as controversial topics as vaccines or masks. They make the air cleaner from smog, smoke, and dust… It’s a great idea overall.”
These boxes are used in classrooms all over the world.
In November 2021, Brown University School of Public Health in Rhode Island Launched a project to build Corsi-Rosenthal Boxes for classrooms and study, and since then the boxes have been installed in many classrooms and student lounges.
UK District Council member Oliver Patrick started GoFundMe last month to provide Corsi-Rosenthal Boxes to schools in his area, He indicated that he was concerned about the lack of public health measures in place in his area.
“I want to make sure we do everything we can to make sure the school is as safe as possible for children,” Patrick wrote.
The California Department of Public Health has listed Corsi Rosenthal funds as Recommended option for classrooms in the February Bulletin to improve air quality in schools to combat COVID-19.
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