Leaving windows open in schools in winter — ‘unrealistic’
There are holes in the Ministry of Education’s prevention measures for SARS-CoV-2, the airborne virus that causes COVID-19. There will always be holes in each intervention measure put in place to prevent transmission. That’s why multiple measures are needed: so that if the virus gets through one, it may be stopped by subsequent measures. A handy metaphor, The Swiss Cheese Model of Pandemic Defense, has been used by virologists to help visualize the effectiveness of multiple measures. Every slice of Swiss cheese has holes in it, the more slices stacked on top of each other, the greater the likelihood that there will not be a way through the stack.
According to COVID Schools Canada [a 100 per cent volunteer-led project tracking COVID-19 cases and outbreaks in schools across Canada], Quebec has the highest student case count of all the provinces. This is hardly surprising given that Quebec’s Ministry of Education has put so few measures in place to prevent transmission. Masks were required for older students, and as the second wave surged, the province provided proper procedural masks to high school students to replace the generally poorer quality masks students had provided themselves. The other significant measure was keeping students in a stable class cohort, but class cohorts are large. Classes with nearly 30 students in the same classroom for most of the day, not wearing masks at lunch, raises the possibility of transmission.
Public health scientists and aerosol scientists advocated that smaller class sizes and good ventilation were also needed. Where ventilation systems couldn’t replace stale air in classrooms quickly enough with fresh air, portable air filters were recommended.
Since most schools in Quebec have inadequate ventilation systems, portable air filters should have been installed in most classrooms.
The province resisted demands for in-class air filters. It instead commissioned a study of classroom air quality by measuring classroom carbon dioxide levels. With every breath CO2 is exhaled. In a poorly ventilated classroom CO2 will build up. The amount of CO2 in a room is a good proxy for air quality; the higher it gets, the worse it is.
According to an article in The Low Down (“Opening windows ‘as good as air purifiers,’” Feb. 3 edition), the Ministry of Education considered 1500 parts per million (ppm) of CO2 acceptable. Jose-Luis Jimenez, a professor of chemistry at Colorado University at Boulder, points out that a CO2 level in a classroom below 700 ppm is considered an acceptable risk, whereas at 800 ppm the room is unsafe, as about one per cent of the air in the room has already been exhaled by students.
Quebec teachers noted that the ministry’s CO2 measurement protocol was unrealistic. Teachers who purchased their own CO2 monitors saw levels far above the ministry’s ‘safe’ level. The protocol seemed to be designed to measure CO2 after leaving windows open — unrealistic given Quebec’s cold winters. In the end, the ministry did nothing to increase ventilation or to filter the air where increased ventilation was not possible.
What it did do, in one case, was require a teacher to remove the portable air filter parents had purchased for their kid’s classroom. On hearing of this, professor Jimenez remarked: “The Quebec Education Ministry wins the prize for the most stupid, ignorant policies. And it is not for lack of worldwide competition!”
Andrew Henry lives in Chelsea, Quebec.