Monitoring ventilation with a carbon dioxide sensor

ALMOST everyone knows that the SARS-CoV-2 virus is airborne, that it could be transmitted through very tiny particles suspended in the air called aerosols. For the longest time, the Department of Health (DoH) got stuck with their "Mask, Hugas, Iwas, Bakuna." But as part of its holiday reminders, the DoH added airflow to its slogan on Covid-19 prevention, probably to acknowledge that stagnant air eases virus transmission. Telling people to open their windows and allow fresh air in is not enough. Aside from getting the vaccines and other interventions, health protocols need to stress the use of well-fitted masks, ventilation and air filtration.

In an article, "With Covid-19, Air Is Both the Problem and the Solution," written by Jonathan Jarry, a question is raised. How is ventilation adequate in any room? To assess potential SARS-CoV-2 aerosols, a nondispersive infrared (NDIR) carbon dioxide (CO2) sensor could be used, suggests Jarry. "You want the air in your house [or indoors] to be as fresh as the outdoor air," added Professor Kimberly Prather, an atmospheric chemist at the Scripps Institution of Oceanography and UC San Diego, who studies aerosols. "We humans breathe air in, hold onto the oxygen, and breathe out CO2. An NDIR CO2 sensor uses a specific beam of infrared light that CO2 molecules love to absorb. The more CO2 in the detector, the less infrared hits the sensor. The device translates this into the amount of CO2 present in the air in parts per million (ppm). When people release CO2 into a shared room, that number creeps up. All that means is that you are breathing other people's shared breaths. We don't want that."