Can CO2 monitors help us get back to normal? Yahoo News Explains

The number of new COVID-19 cases continues to fall in the U.S., and health experts are promoting the use of CO2 monitors as a way to keep that trend going in the right direction as the country begins lifting social distancing restrictions. How would CO2 monitors help restaurants, schools and businesses to reopen? Alex Huffman, aerosol scientist and associate professor of chemistry and biochemistry at the University of Denver, explains.

Video transcript

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ALEX HUFFMAN: Using CO2 monitors, I think, is a really important piece of the process of reopening restaurants and schools and businesses because it's a relatively cheap, easily-used measure of how well the ventilation rate is matched to the number of people in the room. So if there's an infected person in the room, whether they have a mask that is loose fitting or whether they have no mask at all, that person is breathing out infected aerosol.

Think of, like, a smoker. That smoke is coming out of the person, and it's pretty concentrated in one area, but it also wafts across the room. And so after time, it builds up. No matter how far you are away, there's no safe distance to breathing that in.

The idea is that when you breathe out, you breathe CO2 out, as well as aerosols that come out. If we see CO2 start to build up in the room, that means that there's people breathing out in the room, and we're not ventilating it out of the room fast enough to match the number of people in the room. And so we can't measure the aerosols in the room very easily, at least the respiratory infectious aerosol.

We can measure CO2 really easily and relatively cheaply. And so we use this as a proxy for if CO2 is building up, infectious aerosol risk is also building up. So let's do something about it.

So CO2 outside is about 400 parts per million. And so any time it goes above that inside, it's because people are breathing out, and it's starting to build up in that room. But the higher it gets, the more risky it gets because that means aerosol's also building up, and so we'd like to keep it less than 600 ideally. Less than 800 parts per million is good. Once it starts to get above that, the risk just starts to increase.

To increase the ventilation in your house, one of the things you can do is open the windows, the weather permitting, of course. Another simple thing that you can do is just turn on the exhaust fans that you have available, whether it be a bathroom fan or a kitchen fan. Then that pulls air out of the house.

So it's not that hard to put some CO2 monitors in certain places around the establishment for $100 or $200 apiece-- and then if you have some process by which you observe those numbers and then make some decisions and say, if the number is too high, we change our protocols a bit.

Ventilation and room filtration are really important pieces of the puzzle of reducing the COVID risk in any environment. But masking is still critical, distancing away from that person is critical, and also reducing the time that you spend in that place is also critical. Those three things are going to be critical no matter what. And if you're too close to the people, and you're breathing in this cloud, then ventilation is not going to solve the problem.