Almost two-thirds of Brisbane classrooms monitored for air quality have recorded carbon dioxide levels at high risk for COVID-19 transmission, a recent study has found.
The University of Queensland (UQ) study, led by research fellow Stephen Snow, a behavioural scientist, involved placing carbon dioxide sensors in 67 classrooms at different times in 2021 to assess ventilation.
Given the results, Dr Snow suggested all Australian classrooms should have CO2 monitoring to educate students about the importance of ventilation as a public health measure.
"Some schools have obviously been very proactive," he said.
"Air quality management plans exist, but it's not entirely common place."
A citizen science project involving schools, such as Mater Dei Catholic Primary School, at Ashgrove in Brisbane's west, was conducted alongside the UQ study to educate students about improving air quality, both in the classroom and at home.
Year 6 students took part in a workshop in 2021 to build their own indoor air quality monitor as part of the project.
SARS-CoV-2, the virus that causes COVID-19, has thrust the importance of room ventilation into the spotlight, with evidence of it being more readily transmissible through viral particles in human breath than through touching contaminated objects.
The UQ researchers found 42 of the 67 classrooms they studied recorded one or more instances of carbon dioxide levels above 1,800 parts per million – an amount deemed by scientists as posing a high risk of infection if someone in the room has COVID.
Carbon dioxide concentrations in 16 classrooms – almost a quarter of those in the study – remained above 1,800 parts per million for three hours or longer on at least one occasion.
OzSage, an independent group of Australian scientists formed in response to the coronavirus pandemic, advised that CO2 readings above 1,500 parts per million, indicate a "high relative risk of infection".
Classrooms involved in the UQ project came from 13 schools and an early learning centre.
A mix of government-funded, Catholic, and independent schools took part with both primary and secondary school classrooms included.
The worst performing classroom was in a building less than five years old, which was monitored between May and June 2021.
Learning about CO2 levels should be part of curriculum: expert
Carbon dioxide levels in the high school classroom regularly exceeded 3,000 parts per million – amounts at which occupants would be expected to experience headaches, difficulty concentrating, itchy eyes and sore throats, the researchers found.
The UQ study identified factors affecting ventilation such as windows that were forced shut with bolts or screws and difficult-to-reach switches for exhaust fans.
Keeping windows closed to improve energy efficiency was also an issue affecting air quality in some classrooms.
Given the ongoing coronavirus pandemic, Dr Snow suggested the use of carbon dioxide monitors in all classrooms so air quality could be regularly monitored, and measures taken to improve ventilation.
He said learning about carbon dioxide levels and ventilation could form part of the Australian school curriculum, with opportunities to integrate aspects of air quality into maths and science lessons.
"If you've got a CO2 monitor, you're going to have a lot of … monitoring results. You can do statistics on those results," Dr Snow said.
"If you've got data and if you can interpret that data, then you can make better decisions."
He said students could also conduct experiments, such as whether ventilation was better when windows were opened on two classroom walls, versus opening windows on just one side.
Cultural shift required
The UQ researchers called for a cultural shift in Australia regarding indoor air quality, suggesting classrooms introduce regular "ventilation time".
Dr Snow said Australian schools could open doors and windows during recess to routinely ventilate classrooms, pointing out that split system air conditioners do not introduce fresh air.
"It's a different dialogue than we've had before," he said.
"There's a strong energy efficiency argument to keep all the windows closed when you're air conditioning.
"We're going to have to learn moving forward to balance energy efficiency with ventilation considerations.
"If you do need the air conditioner on, close the windows while it's running so the room can cool down, but consider opening doors and windows in between lessons or during lunch, to replace the air in the room."
Students conduct their own studies
Mater Dei Catholic Primary School students say they are much more aware of the need to ventilate indoor spaces after taking part in the UQ citizen science project, dubbed Study Fresh.
Year 6 students helped design and build simple CO2 monitors, then recorded and analysed the results.
Mater Dei student Madeline Carman said the project had benefits beyond the classroom.
"At home, if it's really hot in my room … I'll be like: 'Mum, I think we need to open some windows,'" she said.
"I can see that she has also learnt from our project. She's also been opening windows a lot more in our house now."
Madeline said she could see a benefit for having CO2 monitoring in aged care to help reduce COVID transmission, given elderly people have weaker immune systems.
Mater Dei Catholic Primary School principal Donna Jones said it was "quite alarming" to see how much carbon dioxide was recorded in the school's classrooms at the start of the project.
"It immediately made us talk to the staff … and also the children about what we can do," she said.
"We started to open up our windows and doors and ensuring that we did have that cross ventilation."
Ms Jones said students involved in the project were proactive in reminding other children and teachers about keeping their classrooms ventilated.
"That's been really powerful for them to actually see that they were making a difference in their school and also in their families," she said.
The Queensland Education Department said all state schools had been provided with "at least one" carbon dioxide monitor and guidelines to "assist in managing ventilation within their learning spaces".
"The department has engaged a mechanical engineering firm to undertake ventilation assessments, where required by schools," a statement said.
"Of the 105 schools that have had ventilation assessments completed, the results generally indicate that carbon dioxide levels in classrooms are at acceptable levels.
"As a result of the ventilation assessments, the department has deployed 56 air purifiers to schools and has another 196 stored in locations across the state."
Environmental scientist Donna Green, of the University of NSW, who was not involved in the UQ study, said indoor air quality was not well monitored in Australia.
"One thing COVID has done is make us aware that we need to treat the quality of our air, and the air we put in our bodies, the same as water," Associate Professor Green said.
"We actually need to make sure that the air is healthy for us and is good for our bodies."
