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Oxygen deprevation in the garage

On the show today the guys answered a husband/wife dispute about locking yourself in the garage with your car. It was decided that the catalytic converter on most modern cars is probably good enough to keep you from being poisoned. However, it was proposed that you would die from lack of oxygen since the car is still outputting mostly CO2.

That got me thinking. The engine needs oxygen too. Would the engine die from lack of oxygen before the human? The web claims a human needs about 7% oxygen in the air to survive, but I’m not sure about cars.

Caveat: I’m a humanities major, not a scientist, mechanic, or engineer. Still, here is my take:

Did some surfing. The website contains some fairly recent (2005ish) links to news stories about carbon monoxide deaths from vehicles, so it apparently can still happen. The EPA states vehicles emit about 90% less carbon monoxide than they did before catalytic converters were installed, but that still leaves 10%. And it doesn’t take much CO to kill you, since the stuff binds to your hemoglobin (the stuff in your red blood cells that carries oxygen) MUCH more readily than oxygen. As a consequence, rather quickly, your blood becomes unable to carry oxygen to other parts of your body, such as your brain. So, you fall asleep. Forever.


I think you’re right, it’s not the CO2, it’s the CO, even with a modern car. It’ll take longer, that’s for sure.

What comes to mind is that as the oxygen level in the garage decreased the efficiency of the catalytic converter would go down,they need oxygen to do their thing.

My feeling is a human would be harmed long before the car whould not be able to idle,poorly maybe but still idle.

As the oxygen in the garage gets less it could get low enough that the cars ECM may not be able to adjust the Air fuel ratio enough to keep it idling clean, thus possibly causing incomplete combustion and high CO2. Just a theory.

I’m gonna need a volunteer, a car, and a garage. Any takers?

Carbon monoxide also turns the hemoglobin in your blood an unnatural bright cherry red. A fact that makes CO poisoning obvious to a coroner. The victim’s face is flush and red instead of pale and blue like a heart attack victim.
Meat markets take advantage of this property and use carbon monoxide to keep meat red.

They do make a thing called a combustion analyzer in lieu of a human guinea pig.

Usually the car runs out of gasoline long after the human is dead. Recommend starting car in garage with engine cold; you get more bad stuff than when you drive a hot car into a garage.

I am a retired respiratory therapist and paramedic and it is definitely a bad idea to run a car, new or old, in an enclosed space! CO can cause coma and death in concentrations of 500 ppm. Today’s catalytic converters remove 90% of CO from exhaust, but that leaves as much as 500 - 1500 ppm in the exhaust. CO bonds to hemoglobin 200 times more readily than oxygen, so even small amounts eventually lock up 97% of blood’s oxygen carrying capacity.

It ain’t the oxygen, it’s the Carbon Monoxide. I am an ER doc, and I still see occasional suicides and near-suicides from automotive carbon monoxide sources. The CO may be partially removed by newer catalytic converters such that it takes a lot longer to die, but in an enclosed space the CO will accumulate and will cause altered mental status and eventually death.

I’m actually surprised that this question was posed by an ER doc – She should know this stuff.

Oxygen deprevation even occurs in a smokey bar full of people to the extent of affecting the alcohol/oxygen ratio in the blood. You know dang well it’s never never never acceptable to run a vehicle in an enclosed space !

Years ago, while playing weekends in a local country/rock band, I had always assumed one particular bar had a very poor ventilation system, as I couldn’t seem to catch my breath as well while singing. But I just thought it was me, like a cold comming on or something.
Then one of my co-workers, who had been out to that bar, mentioned to me that he felt more drunk on less beers that weekend. So we initiated our non-scientific research at three different bars over the next couple months.
Sure enough, the same guys with the same number of the same brand of beer would feel their normal buzz at two bars. But at the suspect bar they would get drunk sooner on less beers if they remained inside the building the whole night.
And me, a non-drinker trying to work each place, began to take special notice. I picked one particular song that takes some lung power ( the Brooks & Dunn version of ‘My Maria’ ) and found a substantial difference in my ability to belt out that long chorus. At the suspect bar I would even start to get dizzy and need to cut the note short.

Yes, oxygen deprivation can happen in a very short while in many circumstances you might not normaly suspect.
So when you haven a KNOWN situation, like a car in a garage,…DUH !

Yes, a running car still produces carbon monoxide. Here is a link to a newspaper article from this morning in my area. 4 men went to the hospital with CO poisoning due to a car left running in a garage. Note, these guys weren’t even in the garage but in the adjacent town houses.

Its’ the CO rather than the lack of oxygen.

However, it’s an interesting question. Newer cars do not remove CO from the exhaust, they simply produce less of it because the ratio of oxygen to hydrocarbon is greater, causing more of the “spent” fuel to emerge as CO2 rather than CO. The converter actually raises the CO2 level over what comes out the exhaust port by seperating the nitrogen and oxygen and allowing some of the CO to collect oxygen on the way out and convert to CO2.

The engine won’t die first because it does not use oxygen in the same way.

As long as there is still some oxygen in the intake air commbustion will continue to occur…and if the oxygen were to become too depleated for the ECU to adjust the injector pulsewidth sufficiently to compensate, the engine would simply run rich. Cyliner temps would drop, but the engine would keep running. Ther would have to be almost no oxygen left for the engine to die.

Your body, on the other hand, needs its cells to be able to obtain the oxygen constantly from your bloodstream. If this is not possible due to the oxygen being “bound up”, the cells die. And you go with them.

I respectfully ask Flyingmonkey and Shadowfax this question: does CO2 create a problem in the blood stream? If not, why is two oxygen atoms bound to a carbon atom different than one bound to one?

I didn’t hear the show, but this was a husband/wife dispute. I wonder if the ER doc was warning the other about the dangers, perhaps because he/she (I’m guessing it was a he) was working on the car with the garage door closed, he/she disagreed, and the doc called a car show just to get some backing. There are guys out there that will believe Click and Clack over their MD spouse.

He/she probably even argued that the car would die first anyway so go away and let me work on the car.

Actually it was an ER doc and a resident at the hospital who were having the debate.

CO2 actually is toxic in high concentrations. It’s the probable culprit in mass deaths at Lakes Moulin and Lake Nyos in Africa in the 1980s. It requires pretty high concentrations – 5% or more – to kill people with short term exposure. See