Carbon Monoxide’s Invisible Threat & The Hidden Hazards Of Burning Gas Indoors – CleanTechnica

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During an especially cold spell in late January last year, Lynne from Santa Monica started to feel unwell. “I was just feeling really sick, and I thought it had something to do with the medication I was taking,” she recalls. “I had headaches, nausea, and dizziness — it was pretty bad… My heart was beating like I just ran a marathon. I was just sitting down on the couch and couldn’t catch my breath.” Lynne explored many possible causes for her symptoms, but it wasn’t until she replaced the batteries in her carbon monoxide detector that she discovered what was making her ill.

Cooking and heating with methane gas significantly impacts indoor air quality and are linked to a range of health concerns. In our last article, we highlighted recent research revealing a striking parallel between benzene emissions from gas stoves and cigarette smoke — both sources of unhealthy benzene exposure. But benzene is just one component of a cocktail of hazardous pollutants released during methane gas combustion. Another major byproduct is carbon monoxide (CO), an odorless and colorless gas that can be extremely dangerous. The harmful — and sometimes fatal — effects of carbon monoxide exposure indoors are well-documented in both medical literature and everyday news.

Carbon monoxide can accumulate indoors from multiple sources, with methane gas use being one of the most common. It forms when fossil gas is incompletely combusted. Gas-powered appliances such as furnaces, stoves, fireplaces, and water heaters can all contribute to unsafe CO levels, particularly when they are faulty or poorly vented. Inadequate ventilation and malfunctioning equipment are among the leading causes of elevated carbon monoxide levels in the home.

CO poisoning is one of the most prevalent causes of injury and death from poisoning worldwide. In the United States alone, it leads to more than 20,000 emergency room visits and over 400 deaths each year. Symptoms of carbon monoxide exposure range in severity, from common issues like headaches, nausea, and dizziness, to severe effects such as hallucinations, vomiting, seizures, unconsciousness, and even death. Long-term exposure has also been linked to persistent neurological symptoms, including memory loss, fatigue, dementia, irritability, depression, and movement disorders.

As soon as Lynne replaced her carbon monoxide detector batteries, it immediately registered dangerously high levels of carbon monoxide. When she informed her apartment manager, she was told to open the windows and stop using the furnace until it could be replaced — what turned out to be a malfunctioning methane gas heater. “Literally, the next day, my head felt better. I could breathe better. Since then, it’s been night and day,” she says. Reflecting on the ordeal, Lynne acknowledges how much worse it could have been. “I didn’t smell it . . . I’m not exactly sure how long it was going on. I could have died, without even realizing what was going on.”

Lynne’s testimony is a cautionary story for all of us, and it highlights the importance of vigilance about carbon monoxide exposure indoors. Fortunately, there are several meaningful steps that renters, homeowners, and businesses can take to reduce the risk of carbon monoxide poisoning from indoor gas use. Chief among these is to electrify appliances (furnaces, stoves, water heaters, etc.), as electrical appliances do not produce carbon monoxide. If full electrification isn’t feasible, you can still mitigate risk by improving ventilation, scheduling regular maintenance and checks for gas appliances, following appliance manufacturer guidelines, and properly installing carbon monoxide detectors.

Join us for a webinar devoted to this topic as part of Clean Air Week on September 24, 2025.

This article was written by Wesley Allen and Joe Wachunas.