School ventilation study assessing airborne virus transmission

Air quality monitors have been installed at three New Zealand schools in a bid to understand more about classroom ventilation and airborne transmission of the Delta variant in schools.

Along with testing, vaccination, good hygiene and physical distancing, good ventilation is important in minimising the risk of airborne transmission of the virus that causes COVID-19. The Ministry of Education last week installed CO₂ monitors to gain a stronger understanding of classroom use and related ventilation.

Ministry of Education Associate Deputy Secretary Sam Fowler says the study will build on the Ministry’s knowledge about how CO₂ levels change in different kinds of classrooms throughout the school day.

The monitors have been installed in classrooms at Taupo Nui a Tia College, Epuni Primary School in Lower Hutt and Aurora College in Invercargill by students from Victoria University Wellington and the University of Canterbury. The study is being co-led by NIWA.

Fowler said, “Looking at 18 different classrooms in these three primary and secondary schools will help us understand more about how CO₂ levels change depending on how they’re used and designed.”

He says most schools appear to be doing a good job keeping fresh air moving through their classrooms by keeping their doors and windows open, with only a small number of schools having contacted the Ministry for advice.

“We’ve received advice from our Technical Advisory Group that getting more fresh air in the classroom is the best way to ventilate New Zealand schools to minimise the risk of airborne transmission of COVID-19,” Fowler said.

“We are considering how we can support schools to maintain good ventilation in winter when opening windows and doors can be less practical. This study will give us more information to support our guidance to schools around ventilating classrooms.”

NIWA’s air quality researchers have been studying indoor and outdoor air quality in New Zealand for more than 15 years, including inside people’s homes and in schools. Dr Ian Longley, who’s leading the current study, agrees that natural ventilation – by opening doors and windows – can reduce the likelihood of COVID-19 being transmitted.

“Creating air flow across a classroom removes air from inside and replaces it with clean air from outside, preventing build-up of potentially contaminated air,” said Dr Longley.

“Installing monitors across a number of representative classrooms and combining data from these with information about how the classrooms are being used and ventilated (as recorded by Ministry of Education observers) will give us real data within the New Zealand context as to how different school environments perform.”

The CO₂ monitors NIWA is installing were developed following previous research with Massey University and have been used in a range of indoor air quality studies. They record CO₂ levels every five seconds and transmit the data for rapid analysis by the NIWA team.