When his daughter returned to school in the fall, Dave Pataky said he wanted to minimize the risk of transmission of COVID-19.
Pataky, who has a background in physiology and neuroscience, had concerns about the HVAC system at Walton Elementary School in Coquitlam, British Columbia, so in September he volunteered to create a filter solution air.
He built two Corsi-Rosenthal boxes – a DIY device consisting of furnace filters and a box fan – which he says were used at the school for about three months.
Over the Christmas holidays, he took the boxes home for maintenance and considered building about 25 more for the school. But in January, the local school district told him to put the brakes on his plans.
Pataky said the district told him the DIY filters weren’t approved by the CSA group, formerly known as the Canadian Standards Association.
“I had to give up on the idea,” Pataky said. “So the kids are in their classroom, re-breathing each other’s air, which is the perfect environment for something as contagious as Omicron.”
While vaccines and masking continue to be important in curbing the spread of COVID-19, experts say proper ventilation and filtration are also essential.
Michael Brauer, a professor at the University of British Columbia’s School of Population and Public Health, says opening windows to bring in fresh air can reduce risk, while filters, including homemade Corsi-Rosenthal boxes, are “something that complements the ventilation”.
Pataky said her child’s school has MERV-9 filters — MERV stands for Minimum Efficiency Ratio Value — below the recommended MERV-13 filters. Even if it had better filtration, he says, a Corsi-Rosenthal box could only help.
“Every engineer I’ve spoken to has said any extra filtration in a room is always better,” Pataky said.
In a statement to CBC News, School District 43 said HVAC systems in Coquitlam schools have been inspected and are operating at optimized levels.
“The safety of students and staff is important to us and we expect equipment brought into our schools to meet Canadian safety standards, and homemade units do not meet this standard,” the district said.
HEPA Filter Donation Rejected
After she and her family contracted COVID-19 in September, Elizabete Costa suggested that her son bring his own high-efficiency particulate (HEPA) filter to his classroom at Monterey Middle School in Victoria, which has MERV-10 filters.
She said the teacher and students were happy, but “the morning after dropping off the HEPA filter, the principal took it out of the classroom and put it in a bag in his office.”
When she asked why, she said the principal told her the school had sufficient filtration.
Costa then received a notification about exposure to COVID-19 in the classroom – the same week the filter was removed.
“Even then, they wouldn’t put the HEPA filter back on,” she said.
BC Teachers’ Federation (BCTF) President Teri Mooring says parents who filter schools are a symptom of a bigger problem.
“It’s a pretty sad commentary on our public school system that families and also teachers feel compelled to buy their own HEPA filters to keep schools safe,” she said.
Mooring said BCTF’s assessment of information collected on school ventilation found that “about half of the districts in the province have a lot of work to do on ventilation systems.”
The union has also called for more information on school ventilation systems, which can now be found online.
Mooring said MERV-13 filters are recommended by WorkSafeBC, but MERV-11 filters could be designed to work in conjunction with other items.
$114.5 million spent on ventilation upgrades
The British Columbia Ministry of Education says it has invested $114.5 million to help school districts improve ventilation in thousands of classrooms across the province.
The ministry said a recent survey of 19 school districts found more than 1,500 self-contained HEPA filters were purchased in the latest round of funding.
All public schools in the province conducted regular inspection and maintenance of HVAC systems this year, the ministry said, and it is up to each district to decide where additional supports from families and communities are needed.
The Public Health Agency of Canada says that while HEPA filters can be used as an additional tool, their effectiveness against COVID transmission has not yet been demonstrated and should not replace adequate ventilation, physical distancing and hygiene measures.
Brauer said the Omicron variant is so highly transmissible that stopping transmission is not likely, but measures such as masks and ventilation can help reduce risk. HEPA filters, he said, can be effective if appropriate for the size of the room, and he sees no harm in having them in classrooms.
“It’s hard to imagine how much that would hurt,” he said.