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I keep seeing this conspiracy get repeated. The conspiracy goes like this: car manufacturers don't want homeless people sleeping in cars, so when a car is off, the air vents automatically close. They say you must crack open a window, but this wouldn't be good in the winter time when it's cold, and you can't leave a car running while parked because of the risk of carbon monoxide poisoning. So, a homeless person in the winter time who only has a car would have no choice but to sleep with the car off and the windows rolled up.

Generally when pressed for evidence, this is the article they like to respond with: New Zealand couple manages to lock themselves in keyless car for 13 hour

Is a person at risk of suffocation from oxygen deprivation if they sleep in their car with the engine off and the windows rolled up?

Laurel
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Willy150
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    Hi Mike, great question, but would you mind clarifying whether you're more interested in evidence "that it is possible to die of CO poisoning in a closed, running car", or that * "car manufacturers actively make changes to their vehicles to prevent people from sleeping in them safely?" * thanks a lot! – 0xDBFB7 Dec 16 '21 at 19:47
  • Hi, I'm not talking about CO poisoning, but oxygen deprivation from being in a car that is not running, with the windows rolled up. – Willy150 Dec 16 '21 at 19:50
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    There are two distinct claims here. One is that little or no outside air enters a car which is not moving and whose systems are turned off. This is true to a large extent: without either a fan or pressure due to the car moving forward, very little air actually moves through the ventilation system. The question is whether this is so little that one person could suffocate overnight. The other claim, for which you don't show a citation (you should), is that there is some kind of far-fetched conspiracy in which manufacturers make this specific situation worse than it _naturally_ is. – Gilles 'SO- stop being evil' Dec 16 '21 at 20:05
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    And a third claim is that the CO emissions from a modern car are dangerous. It is extremely rare for carbon monoxide poisoning to occur in a modern car. It would almost certainly be because there is a fault in the exhaust system. Iowa State University [claims](https://www.abe.iastate.edu/extension-and-outreach/carbon-monoxide-poisoning-vehicles-aen-208/) that about 1,000 ppm CO is emitted from gasoline engines with a catalytic converter, compared with 30,000 to 100,000 ppm from engines without. – Weather Vane Dec 16 '21 at 21:52
  • @WeatherVane https://arstechnica.com/cars/2014/12/new-zealand-couple-manages-to-lock-themselves-in-keyless-car-for-13-hours/ would this have been a case of carbon monoxide poisoning? The article doesn't go into detail about why they were having trouble breathing. But the articles mention that the wife, who was found unconscious, had to subsequently be hospitalized for three days after they were found. – Willy150 Dec 16 '21 at 21:54
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    The linked story mentions neither carbon monoxide, CO nor poison. The phrase "the risk of carbon monoxide poisoning" is a claim that you have made yourself. – Weather Vane Dec 16 '21 at 21:57
  • @WeatherVane I know that. It doesn't mention why the wife was unconscious or why the husband was having trouble breathing. The news article provided makes no sense and I'm not sure if it's made up or true. – Willy150 Dec 16 '21 at 22:02
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    Well, if the car's engine had also magically started in the absence of the key, don't you think that would have been mentioned? – Weather Vane Dec 16 '21 at 22:21
  • @WeatherVane The article doesn't mention why the overnight stay in the car made them come close to death. If the article refuses to clarify on such crucial details, perhaps the car being on would also be left out. This news article seems more like an urban legend than fact as I am unable to verify it. – Willy150 Dec 16 '21 at 22:24
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    "*They say* you must crack open a window": You'd think they would say it pretty prominently, to avoid being sued by someone who didn't know this and hypothetically died. But I don't believe I've ever seen anything of the kind in any owner's manual, have you? – Nate Eldredge Dec 17 '21 at 02:54
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    There are lots of reasons they could have had breathing trouble, unrelated to suffocation. Panic attack due to claustrophobia, dehydration, existing medical problems that they didn't have their medication for, etc. – Nate Eldredge Dec 17 '21 at 02:58
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    Can we get a better notability reference? Perhaps three or four people actually making the claim. – Oddthinking Dec 17 '21 at 06:21
  • As @Oddthinking and Nate point out, there is no notability reference stating that fresh air supply is shut off when the vehicle engine is off. Where did you see that air vents close and therefore the car is sealed from any incoming air? – Chris Rogers Dec 17 '21 at 08:26
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    Do any of these claims state why they don't like homeless people sleeping in cars? – Joe W Dec 17 '21 at 16:01
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    There's no notable claim here. The linked story says absolutely nothing about the claim, leaving us to speculate about why the woman was unconscious. For all we know, she may have been diabetic and had no access to her medication. The OP says "I keep seeing this conspiracy get repeated" - can you provide a link to one, or several, of those claims @MikeSmitt? – Mark Dec 17 '21 at 16:37
  • **_DO NOT SLEEP IN A CAR WITH THE WINDOWS UP AND AC OFF!!_** I'm not going to write an answer because I hate morbid topics. But, seriously, after some searching, I've found numerous sources that claim it's safe; it's not. – Nat Dec 18 '21 at 09:31
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    A few points to consider, though I do not have sources at the level required for an answer. a) truck drivers regularly sleep in their cabin with windows closed. However, one may argue that the truck cabins are meant for sleeping and therefore are properly ventilated and not suitable to check the claim. b) I'm in Germany. When there's a really bad traffic jam, the police may advise that you can sleep and they'll come along to wake everyone shortly before things will be moving again. They advise to switch off motor and all electric devices (so the battery won't run low). (In winter, the red... – cbeleites unhappy with SX Dec 18 '21 at 16:57
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    ... cross may come along and distribute blankets and hot tea.) I've never heard them advise to keep the windows open. c) Environmental laws over here prohibit leaving the car idling when parked. And leaving the motor on without a (wake) driver is anyways a safety risk of its own. d) Anecdata: while I prefer to sleep with windows and even doors wide open to prevent the buildup of moisture whenever the weather allows (like I prefer to leave the tent door open), I and a number of friends/acquaintances have slept many nights in cars with doors + windows closed without any ill effects (other than – cbeleites unhappy with SX Dec 18 '21 at 17:02
  • ... moisture). Sure, that's usually vans with enough space to properly stretch out. e) There are cars/trucks where the cargo compartment is not ventilated like a cabin for driver/passensers. I would treat them differently in terms of keeping the door open, but you can easily recognize them by the warning label that says the compartment is sealed so expect over/underpressure when opening the door. – cbeleites unhappy with SX Dec 18 '21 at 17:06
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    Data point: Two of us, small car. No apparent harm. (We gave up on finding our objective in the dark, simply parked and slept until daylight.) – Loren Pechtel Dec 20 '21 at 03:30
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    @Nat - I have slept many times in cars, engine off, windows shut. Sometimes on my own, sometimes in company. Sure, you end up with condensation fairly rapidly, but there is absolutely no problem with getting enough oxygen. – Rory Alsop Dec 21 '21 at 12:57
  • @RoryAlsop: It's not generally a huge problem. That said, there're smaller issues, e.g. higher organic-volatiles that don't vent so well (lots of glues/preservatives in some cars) and higher CO2 concentrations can stress metabolisms, with somewhat complex consequences. Still, yeah, overall it's generally not too bad for one or two people to sleep in a car, especially if there's wind and the occupants are in good health. – Nat Dec 21 '21 at 14:13
  • @RoryAlsop: That said, in windless environments (possibly outside, especially in locations like indoor parking-garages), transport can be dominated by more diffusive effects, where the net flow is proportional to the concentration difference between inside and outside (for each component individually). Additional folks take a larger share, driving down the internal concentrations of O2 and up CO2. Plus, depending on some somewhat complex factors, CO might be problematic. – Nat Dec 21 '21 at 14:17
  • @RoryAlsop: Then there're cases where, say, snow falls while folks are sleeping. Or there's a frost and a sheet of thin ice freezes over. Or the car's older and has internal-fouling in the vents, where degraded material significantly increases the resistance. Or an occupant has COVID and might be unaware of their vulnerability to reduced O2. Or something like Telsa's "_bio-defense mode_" (or whatever it was called). – Nat Dec 21 '21 at 14:18
  • @RoryAlsop: Overall, sleeping in cars is probably a not-so-good thing to do (due to pollutants and increased biological stresses), and then there'd be cases where we'd have larger concerns. – Nat Dec 21 '21 at 14:22
  • Why do you think there are increased biological stresses or pollutants? I think in general your previous 3 comments are just speculative. Along the lines of "parking in front of a lava flow, or next to an eroding cliff could be problematic" – Rory Alsop Dec 21 '21 at 14:29
  • @RoryAlsop: I'm not really sure what specific point to address. [This website](https://www.autogeek.net/voc-compliant.html) might help with some intro to the concern with pollutants. The other concerns aren't speculative so much as concerns that we'd want to have managed, which might be hard for folks who aren't aware of them. – Nat Dec 21 '21 at 14:53
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    @Nat, so of that list, none would be inside any car I own. And only fuel would be outside (well, in the tank) - again, this seems to be a "if you put pollutants inside your car they will be inside your car" issue. I think I'm done with this – Rory Alsop Dec 21 '21 at 16:33
  • @RoryAlsop: I think you're misunderstanding some stuff. For example, your car almost certainly has such pollutants in it. Organic-volatiles commonly come from stuff like foams, glues, paints, preservatives, and so forth. – Nat Dec 21 '21 at 16:56
  • @RoryAlsop: [Here's a link for new cars.](https://www.webmd.com/men/news/20120215/is-that-new-car-smell-toxic) That said, folks might think that once the "_new car smell_" goes away, that's it, but that isn't the case due to material-degradations, especially in warmer climates. – Nat Dec 21 '21 at 17:03
  • Let us [continue this discussion in chat](https://chat.stackexchange.com/rooms/132534/discussion-between-rory-alsop-and-nat). – Rory Alsop Dec 21 '21 at 20:27
  • If you used up all the oxygen in the cabin, you would wake up and feel the lack of oxygen. Humans can't detect asphyxiants like carbon monoxide or helium, but we *can* detect a build-up of carbon dioxide, which is what would be happening. https://medicine.uiowa.edu/content/specific-neurons-trigger-waking-due-inhaled-co2 – endolith Feb 19 '22 at 19:22

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According to Measurement of air exchange rate of stationary vehicles and estimation of in-vehicle exposure (1998):

The air exchange rates or air changes per hour (ACH) were measured under 4 conditions in 3 stationary automobiles. The ACH ranged between 1.0 and 3.0 h-1 with windows closed and no mechanical ventilation

The air in a parked stationary car is fully exchanged every hour or so at the worst (through the passive vents in the car). That is more then enough to keep CO2 and O2 levels OK, and you're not in any more danger of asphyxiation in a car that's off than in a bedroom with the windows closed and door shut.

I don't have a good way to rebut the "cars will shut those vents to murder their occupants" part of the conspiracy theory. It's hard to prove a negative. That said, car manufacturers are unlikely to be in a conspiracy to kill their customers, and I think most people have at one time or another slept a few hours in a car (and survived).

CJR
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  • Comments are not for extended discussion; this conversation has been [moved to chat](https://chat.stackexchange.com/rooms/132610/discussion-on-answer-by-cjr-is-sleeping-in-a-car-with-the-windows-rolled-up-dang). – Oddthinking Dec 25 '21 at 20:02