Toronto residents may soon be able to rent out a carbon dioxide (CO2) monitor at the public library as part of the city’s pandemic response.

In April, the City of Peterborough became the first municipality in North America to facilitate such a program—lending out CO2 monitors to residents for a week at a time so they could determine the quality of air ventilation within their home, office, or other indoor spaces.

The devices use a “stoplight system,” officials said at the time. A green light means the air quality in the space is good, yellow means it is okay, and red means there is little ventilation in the area.

The higher the CO2 levels within the space, the more recycled air an individual will be inhaling.

“Good ventilation and filtration are important because it helps decrease the risk of illness by reducing the levels of aerosols containing viruses and bacteria, and other air quality concerns, that can make us sick, including the virus causing COVID-19,” Dr. Thomas Piggott, Peterborough’s medical officer of health, said in a statement issued in April.

Piggott added that it’s relatively easy to lower levels of CO2 if residents get a high result. Actions such as opening windows, reducing the number of people in a room and using air filtration devices will all help with increasing air ventilation. Mask wearing will also help remove potential pollutants in the air.

Around the same time that Peterborough’s program launched, some residents reached out to the Toronto Public Library inquiring if they had plans to do something similar. At the time, officials said on social media that they were contacted by organizations interested in donating CO2 monitors and that updates would come at a later date.

Months later, it appears as though a formal program may be underway.

In a tweet posted on July 2, the library said they plan on introducing a CO2 monitor program in mid-July and more information is expected “in the coming weeks.”

CTV News Toronto has reached out to the library for further details.

CO2 monitors have been widely used throughout the pandemic, although not consistently. In 2021, Quebec’s education minister said that monitors would be installed in every classroom.

Yet, when an Ontario Public Health Unit tried to enforce a policy in which any classroom with a CO2 reading of more than 800 parts per million receive an additional HEPA air filter, the province’s chief medical officer of health said experts were “not aware at present of any correlation between CO2 levels and viral transmission.”

The use of CO2 monitoring has been widely proven in scientific journals as a tool to measure risk of COVID-19 infection.