do cars release carbon monoxide

[CourtneyMarie]

Yes, cars that burn gasoline or diesel do release carbon monoxide (CO). This harmful gas is a direct product of the incomplete combustion of fuel within the engine. When there isn't enough oxygen present during the burning process, the carbon in the fuel doesn't fully convert to carbon dioxide (CO2) and instead produces CO. This is why properly functioning emission control systems, especially the catalytic converter, are critical, as they chemically transform most of this toxic CO into less harmful CO2 before it exits the exhaust.

The primary danger of carbon monoxide is that it is colorless, odorless, and can be fatal in enclosed spaces. Never run a vehicle's engine inside a garage, even with the door open, as CO can quickly accumulate to dangerous levels. While all internal combustion engine vehicles produce some CO, modern cars are subject to strict emissions standards that have drastically reduced their output compared to older models.

The following table illustrates the dramatic reduction in carbon monoxide emissions for gasoline passenger cars in the United States, as regulated by the Environmental Protection Agency (EPA).

Model Year	EPA Standard for CO (grams per mile)	Notes
Pre-1968	Unregulated	Vehicles had no significant emissions controls.
1975	15 g/mile	Introduction of the catalytic converter.
1981	7.0 g/mile	Stricter standards under the Clean Air Act.
1994	3.4 g/mile	Further tightening of regulations.
2004	1.7 g/mile	Tier 2 standards began phasing in.
2017+	1.0 g/mile	Tier 3 standards significantly reduced allowable CO.

It's also important to distinguish between tailpipe emissions and cabin air quality. A well-maintained car with a intact exhaust system poses virtually no risk of CO poisoning to occupants while driving. However, any damage to the exhaust system or a faulty cabin air seal could potentially allow exhaust gases, including CO, to enter the vehicle's interior. Symptoms like sudden dizziness, headache, or nausea while driving warrant immediate attention and inspection of the vehicle.

[SanDelaney]

Absolutely. That’s the main reason you should never warm up your car inside a closed garage. The engine burns gas, and if it doesn’t burn it completely—which it never perfectly does—it makes carbon monoxide. It’s silent and invisible, which is what makes it so dangerous. Newer cars are much cleaner, but the rule remains the same: always pull your car out into the open air before letting it idle for more than a minute.

[BrookeRose]

They do, but the amount is tightly controlled. My focus is on the environmental regulations that have forced manufacturers to innovate. Since the 1970s, standards for carbon monoxide and other pollutants have become progressively stricter. The widespread adoption of the three-way catalytic converter was a game-changer, effectively breaking down over 90% of CO emissions. While not zero, the output from a modern vehicle is a fraction of what it was decades ago.

[OSavannah]

It's a key reason for emissions testing in many states. When you take your car for its annual inspection, they measure the exhaust to ensure the catalytic converter is working properly. If that system fails, carbon monoxide levels can spike. A strong smell of exhaust or black smoke from the tailpipe are clear warning signs that the engine isn't running cleanly and is likely producing excessive CO, which is bad for both public health and your engine's efficiency.

[CoraDella]

Yes, and it's a critical safety issue beyond just pollution. I think about it from a family safety perspective. We install carbon monoxide detectors in our homes, but we should also be aware of the risks from our vehicles. A blocked tailpipe from snow or a faulty exhaust leak into the cabin can have tragic consequences. It’s a reminder to keep your car well-maintained and to never ignore symptoms like a headache or drowsiness while driving, which could indicate a CO leak.