Aircraft have HEPA filters which help to remove impurities and viral particles from the air. However, many buildings lack any form of air filtration, which requires air to be manually refreshed.
A federal study in 2019 found that two thirds of Swiss classrooms were insufficiently ventilated. In some cases the air towards the end of the school day was so poor it would be expected to affect student performance – high levels of CO2 make people sleepy.
Six air changes an hour are recommended for a 9 m2 room with 3 or 4 people in it. One study suggests a rate of nine times per hour reduced the spread of SARS, MERS and H1N1 in a Hong Kong hospital.
To increase the chance of schools and offices refreshing the air in their buildings the Swiss National COVID-19 Science Task Force is recommending building managers install CO2 meters that signal when the air quality has reached an unhealthy level.
Science Task Force argues that CO2 sensors represent, particularly in schools, an underutilised, low-hanging fruit in the fight against the Covid-19 pandemic. The idea is to avoid breathing air that has been in someone else’s lungs and CO2 is a good measure of this.
However, CO2 monitoring is not perfect. Singing, shouting, strenuous physical exercise, all activities with high aerosol emission, could create high aerosol concentrations even when CO2 levels are acceptable, wrote the task force in a report.
Government report (in English)