I Measured the Pollution From My Gas Stove. It Was Bad.

Here's what I learned putting air quality monitors all over my house.

In December, researchers published a study that found gas stoves are responsible for 12.7% of childhood asthma cases in America. The new data suggests that about 650,000 cases of asthma can be attributed to the methane-burning appliances that sit in more than a third of U.S. kitchens.

But this isn’t the first study proving a link between gas stoves and asthma. Researchers have been studying the link between indoor air pollution and human health for more than 50 years. With each new study, it becomes more clear that gas stoves are dangerous. 

About a year ago, I decided to dive into this research and learn more about the health and climate impacts of gas stoves. I spent dozens of hours reading through academic studies on gas stoves dating back to the 1970s and interviewing experts. I also put air quality monitors all over my house and ran my own amateur experiments to see how much indoor air pollution my gas stove produced over that period. 

The results of all this research were, frankly, disturbing. 

A brief history of indoor pollution research

Research on air pollution and human health began in earnest in the middle of the 20th century. But it wasn’t until the 1970s that researchers began to turn their attention indoors. Many of these researchers hypothesized that just as power plants and gas-combustion cars produce harmful levels of pollution outside, activities like smoking cigarettes and using gas appliances produce harmful levels of pollution inside. 

Early studies on the link between gas cooking and human health came with mixed results though. In 1973 researchers in England and Scotland surveyed the parents of 5,658 children and found a positive correlation between gas cooking and asthma symptoms. Later that decade, the same researchers surveyed 390 infants born between 1975 and 1978. This time they found no correlation between respiratory illness rates and cooking fuel. 

But as researchers produced more studies, the link between gas stoves and respiratory illness became more clear. In 1992, the EPA analyzed results from dozens of studies in the first meta-analysis on the topic. They concluded that the nitrogen dioxide (NO2) produced by a typical gas stove was enough to increase a child’s risk of asthma by 20%. 

Over the next two decades many studies confirmed this finding. By 2005, there was enough evidence to convince the World Health Organization (WHO) to recommend limiting nitrogen dioxide exposure for the first time.

In 2013, a meta-analysis found, “Children living in a home with gas cooking have a 42% increased risk of having current asthma.” 

Yet, despite all this evidence, the EPA hasn’t issued their own guidelines on indoor air pollution. More than 10 million homes have been built since the WHO published their first indoor air pollution guidelines. Roughly a third of those homes have a gas stove in them. Each time the people living in those buildings click on the burner, they’re slowly damaging their lungs. Most of them have no idea.

A little at-home science experiment

About a year ago, I installed air quality monitors throughout our house and began running my own experiments on indoor air pollution. Every night, as we turned on the gas stove or heated up the oven to cook dinner, NO2 levels in both our kitchen and bedroom spiked.

(One quick note: Sometimes you’ll see NO2 measured in micrograms (one-millionth of a gram) per cubic meter or µg/m3. Other times you’ll see it in parts per billion or ppb like the graph above. The conversion is [ug/m3]/1.88 = 1 ppb. Very annoying, I know). 

There was one day of the week that NO2 levels didn’t spike, however. Every Tuesday we get takeout and, unsurprisingly, on those nights, NO2 levels were much lower. 

The holidays offered another opportunity for testing. On Christmas Eve, we went to the mountains to visit my family for a night. When I looked at the air quality monitor data for that day, I saw that our NO2 levels were lower than any other day in the month. 

At first I figured it was because we weren’t cooking anything. But then I realized that if that were true, NO2 levels would have plummeted like that every Tuesday when we didn’t use our gas stove. 

When I spent more time looking at the data, I noticed something strange. In almost every 24 hour period, our NO2 levels were the highest between about 2am and 7am. Unless my wife was sneaking out of bed for midnight snacks, something was amiss. 

I looked at the energy usage data from our Nest thermostat and discovered that those levels corresponded almost exactly with the times that our gas furnace was on. I reached out to a friend who used to work as an energy auditor and he told me that any number of things could be causing this. Our furnace could be venting improperly. Or maybe it was our water heater. Or a change in air pressure caused by the furnace could be causing the water heater to vent improperly. 

That same week I had an energy auditor come out to our house through our utility’s rebate program. When I asked them about the NO2 levels, they said they didn’t have the equipment to measure it. They only focus on the stuff that kills you quickly like carbon monoxide, not the stuff that wreaks havoc on the human body slowly over the course of years. 

Shortly after the audit I sent some of the data from my tests to Josiah Kephart, an environmental epidemiologist at Drexel University. In an email he wrote, “I would say you’ve got a pretty big NO2 problem. Your daily averages are double the [WHO] daily guideline.” 

Kephart has spent most of his career running air quality experiments. He told me that often when he or his peers discover high levels of indoor air pollution the gas industry blames the homeowner. They say the homeowner isn’t using their ventilation properly or someone didn’t install the stove correctly. 

But he said there’s a problem with this logic. “I don’t care about how the system is supposed to work, I care how it really is working in real life,” Kephart said. “What we see when we actually test these things in real life are high levels of indoor NO2 everywhere we look.”

In other words, it may be possible to build a home with perfectly vented gas appliances, and there may be a safe level of NO2, but in the real world—in the homes that we all actually live in—this is probably the rare exception. The more likely norm is unused range hoods, furnace flues that spill chemicals into the air we breathe, and ultimately higher rates of illness. 

I began this research as a skeptic. Why? For the same reasons you may be skeptical right now. Accepting that a gas stove or any other fossil-fuel appliance makes a home less healthy isn’t simply an abstract intellectual exercise. It has practical consequences like forking up the time and money to replace the thing — an option that, like so many other health improvements, isn’t available to all. 

But as I’ve learned more about this topic, my skepticism has faded. Every rigorous review of the research points to the same conclusion: Most homes with gas stoves have unsafe levels of nitrogen dioxide and that results in higher rates of respiratory illness. 

This story was originally published in January 2022. It has been edited slightly for clarity and to reflect new research. 

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