My boyfriend was not feeling well. Again, that wasn’t too surprising.
We had just spent a weekend at the annual New Orleans Jazz Festival, where we spent long days cooking in the 90 degree heat and drinking lots of beer to stay cool. But hangovers and heatstroke weren’t the only potential culprits.
The risk of COVID was everywhere. I knew this because for weeks I had been carrying around a $150 palm-sized carbon dioxide monitor that rates just that.
Then Jesse told me he didn’t feel anything. A bright pink line soon confirmed the answer I dreaded. He had COVID. Three days later – after two years of avoiding it – I also tested positive.
Carbon dioxide monitors can assess a space’s COVID risk because they help you know if you’re breathing clean air. They measure the concentration of carbon dioxide, which people exhale when they breathe, as well as other things like, potentially, virus particles. The better ventilated a space, the lower the reading on my monitor screen, which not only means less carbon dioxide, but also less of things like COVID that could make people sick.
I had tested the device because I was curious how useful technology like this could be in the midst of a global pandemic when we are all making decisions about aspects of pre-pandemic life to resume and where to continue to exercise caution. I also wanted to see what it might reveal about the safety of the places where I spend my time. More often than not, I found the number on my monitor screen to be high – too high.
I’m not the only one who had this idea.
“Because masks are no longer needed, I find myself using a carbon dioxide sensor more,” said Linsey Marr, an aerosol scientist at Virginia Tech who’s had a monitor for about a year and a half. “I feel like I now have a much better sense of ‘Oh, this place could be risky, and this one less risky’.”
In a perfect world, carbon dioxide levels would be readily available in every space, allowing us to better understand the unseen infrastructure that determines the safety of our environment as we tackle the delicate task of finding a new normal. . Instead, we’re stuck navigating this new phase of the pandemic with no real sense of the real risk from our offices, favorite restaurants, or local movie theaters.
The CO2 monitor accompanied me not only to New Orleans (where carbon dioxide readings ranged from 636 parts per million to 4325 ppm), but also to a Passover family seder in Illinois (less than 1,000 ppm), at wine tastings in Oregon’s Willamette Valley (441 ppm to 722 ppm) and, after the transport mask mandate ended in mid-April, on plane rides filled with newly without mask (about 585 ppm to 1,928 ppm).
The monitor frequently displayed a number above the Centers for Disease Control and Prevention’s recommended benchmark for indoor air quality of 800 ppm – in fact, about 60% of my readings over the course of a month exceeded that number.
In restaurants, in taxis and on planes, I have seen the numbers climb to worrying levels, but also in people, in a hotel room and in a store. Sometimes the readings were several times higher than 800 ppm.
These numbers were a signal not only that I was in poorly ventilated spaces, but also that I was breathing in the potentially COVID-laden air that other people were exhaling. At one point, while I was in a car with the windows closed and the air conditioning on, almost 10% of what I breathed in had been exhaled. My carbon dioxide monitor tells me exactly how much is going on.
If you’re in a space with high levels of carbon dioxide, Marr says, you might want to put on a high-quality mask or try to minimize the time spent there.
Some of the highest readings in my travels were taken when boarding the flights I was on. Although you hear a lot about aircraft filtration, these systems often don’t work until the plane starts moving.
“We warned about this,” said Joe Allen, associate professor at Harvard TH Chan School of Public Health and another public health expert wearing a carbon dioxide monitor.
The carbon dioxide monitor readings were also high in flight, but this turned out to reflect one of the limitations of the device: it measures ventilation, but not filtration. Air on airplanes is recirculated, so you breathe in a lot of air that other people have exhaled, but that air also passes through a high-quality filter, so it’s unlikely to contain virus particles. , Marr said.
Limitations aside, my device’s readings were consistently high in many types of locations. Allen said that’s because good ventilation isn’t usually a high priority – although he sees that changing now, two years after a global pandemic killed more than a million Americans. Improving indoor ventilation doesn’t have to be difficult or expensive either. It can be as simple as opening windows or installing high-quality filters in an existing HVAC system.
And fresh air doesn’t just reduce the risk of COVID. It can also help reduce contaminants that build up from things like pet allergens, mold, and chemical cleaners — all things you don’t want to breathe in either. There’s even a name for the disease caused by poor ventilation: sick building syndrome.
Places I haven’t been able to get to on my travels, like Boston Public Schools (where Allen served as a ventilation consultant) and entertainment venues in Japan, make air quality information more widely available. Belgium has gone even further by requiring visible carbon dioxide monitors in public places.
Meanwhile in the United States, the Biden administration has only said that businesses and organizations should take action to improve indoor air quality. But these are only recommendations, and the administration has not set specific standards for air quality or provided dedicated funding to help with broad improvements.
Yet the new focus on indoor air quality may help grow the global market for technologies that can monitor indoor and outdoor contaminants. This market is expected to grow from $4.4 billion to $6.4 billion by 2028, according to New York-based Zion Market Research.
Ventilation is not the only factor that influences risk, but it is one of the easiest factors to change. It is also less severe than other COVID measures like, for example, restricting indoor capacity. (Allen said vaccination status, time spent in a location, and size of a space also matter.)
And sharing this information with the public can give us a better understanding of the risks we take as we live in a world where a highly contagious virus surrounds us.
The instructor also showed me which places were safe enough. Like outside, where levels stayed low even at the crowded Jazz Fest. Airports were surprisingly well ventilated, as was a hotel lobby, especially compared to the upstairs hotel room. The high-ceilinged and mostly empty cellars in Oregon where my friend and I did tastings also had great reads.
No one can know exactly how they contracted COVID, but after a month of monitoring carbon dioxide levels, I had a pretty good idea. Most of Jazzfest is outdoors, but on our first night in New Orleans, we had tickets to a concert of my boyfriend’s favorite band.
We got to the show early and stopped at the bar. The space was still relatively empty. I pulled out my carbon dioxide monitor and checked the reading: 641 ppm. Not bad. Well below the CDC benchmark of 800 ppm.
Soon the hall filled with people singing and dancing. My monitor died, but based on all the readings I had taken so far, I could easily imagine those numbers were way over 800.
Shortly after, one of the musicians who played that night shared publicly that he had COVID-19. And a few days later, we had it too.