CO2 as a proxy

Carbon dioxide is generated by the natural nature of our being; every time we release carbon dioxide in the form of aerosols. In the current pandemic, such aerosols could contain SARS-CoV-2 by COVID-19-infected people.

Hence, carbon dioxide can be used as a proxy of SARS-CoV-2 concentrations indoors. Your risk of being exposed is 20x higher in indoor settings. It is for this reason that ventilation is an essential mitigation, along with masks. In an ideal world, all activities would take place outdoors. Unfortunately, thats is not a practical solution.

According to a research paper titled,

” Exhaled CO2 as COVID-19 infection risk proxy for different indoor environments and activities”

Authors: Z. Peng1 , J. L. Jimenez1*.”

⚠️ The relative infection risk in a given environment scales with excess CO₂ level, and thus, keeping CO₂ as low as feasible in a space allows optimization of the protection provided by ventilation.

This begs the question.
If we accept there are unavoidable indoor activities (school, offices, hospitals, hotels, beauty shops, public transport and so forth), how do we reduce our risk?

Scenario: A school classroom , with windows that open, which holds 28 students plus a teacher.

In a poorly ventilated room, the CO2 levels would gradually build to unsafe levels for infection control and for productivity. The current solution is to merely open a door and a window. Unfortunately, hope is not a strategy.

Activities that generate more aerosols:

• merely the act of talking
• singing
• laughing
• exercise relate breathing

A key strategy is to ensure you are keeping CO2 levels at lower/acceptable levels (below 800ppm) which by implication, infers adequate ventilation, is to measure the indoor air.
Based on the data, one can take the appropriate action for that particular location.

                          What gets measured, gets managed

The benefits?

• exposure risk reduction by ensuring adequate ventilation
• ventilation coupled with filtration is a complimentary mitigation layer
• empowering of staff and students in their space
• transparency of mitigation by displaying measurements and guidelines
• strategic insight of problematic spaces that require an upgrade
• increased parental confidence in management