When Alex Huffman, an aerosol scientist and associate professor at the University of Denver, recently outfitted his house with CO2 monitors—part of a home experiment to see how well different spaces were ventilated—he found out his home was pretty tightly sealed against the outside air, but carbon dioxide exhaled from his family would build up a bit as they lived their lives. There was a bigger surprise, though: When they cooked, the CO2 levels skyrocketed—not only in the kitchen, but throughout the house.
“I was amazed to see how high the CO2 went,” Huffman says, noting that his home has no externally venting fan. “The CO2 built up very quickly and stayed high. As long as we didn’t open the windows, it stayed high for hours.”
Huffman was monitoring CO2 not out of environmental or health concerns, but as a proxy for COVID-19 transmission. When we breathe, we exhale both CO2 and aerosol droplets, so the concentration of CO2 in a space can give you an idea of how many aerosols, which may contain COVID-19, have built up. But CO2 is also a pollutant, and the readings he got when cooking show how polluting the activity is.
Cooking emissions also contain small particles known as PM2.5 (particulate matter smaller than 2.5 micrometers). These particles, which are also prevalent in wildfire smoke, can penetrate into our lungs and even enter our bloodstream. They can make asthma more severe, worsen chronic lung conditions such as COPD and emphysema, and there’s also evidence these particles can increase heart attacks, strokes, and lead to premature deaths. High CO2 levels cause health effects too, such as rapid heart rate, headaches, fatigue, dizziness, and nausea. The burning natural gas in gas stoves also produces amounts of nitrogen dioxide, another potent pollutant.