When you shut off your car, do your air vents intakes close?
Discussion
I mean the vents that intake fresh air from outside to feed to the cabin. A couple in New Zealand claim they got locked inside their brand new Mazda which was parked in a garage, with the engine off, and the windows rolled up. They were in the car from seven pm at night to seven pm in the morning.
https://www.carscoops.com/2014/12/couple-trapped-i...
They tried to break the window but couldn't, and they couldn't turn on the engine to open up the vent because they didn't have the key fob. When they got inside the car, it automatically locked, then they remembered they didn't bring the key fob inside with them.
By the time they were found they were almost dead from oxygen deprivation.
There's limited studies on ventilation in stationary cars that have the vents open but the one I found said the air exchange rate is about 10-20~ times per hour if the vents are open, obviously faster if the fan is running, but as low as 0.01~ air changes per hour if the vents are closed. So with new cars at least, when the vents are closed, too little air comes inside.
The studies showed an air exchange rate of ~10 times per hour was more than enough to sustain four people and carbon dioxide levels didn't rise at all. But when the vents were shut, carbon dioxide rose to unhealthy levels (over 10,000 ppm!) very quickly. In these tests the cars were stationary and the windows were up. Since their car was off I'm wondering if the vents were automatically closed, and if this is just a one off thing or if it's normal for most new cars to do this. Also if this is the case, why automatically shut the vent when the car is off? Shouldn't it be considered a hazard in case people accidentally end up locked in the car and can't escape? Is this a design flaw?
https://www.carscoops.com/2014/12/couple-trapped-i...
They tried to break the window but couldn't, and they couldn't turn on the engine to open up the vent because they didn't have the key fob. When they got inside the car, it automatically locked, then they remembered they didn't bring the key fob inside with them.
By the time they were found they were almost dead from oxygen deprivation.
There's limited studies on ventilation in stationary cars that have the vents open but the one I found said the air exchange rate is about 10-20~ times per hour if the vents are open, obviously faster if the fan is running, but as low as 0.01~ air changes per hour if the vents are closed. So with new cars at least, when the vents are closed, too little air comes inside.
The studies showed an air exchange rate of ~10 times per hour was more than enough to sustain four people and carbon dioxide levels didn't rise at all. But when the vents were shut, carbon dioxide rose to unhealthy levels (over 10,000 ppm!) very quickly. In these tests the cars were stationary and the windows were up. Since their car was off I'm wondering if the vents were automatically closed, and if this is just a one off thing or if it's normal for most new cars to do this. Also if this is the case, why automatically shut the vent when the car is off? Shouldn't it be considered a hazard in case people accidentally end up locked in the car and can't escape? Is this a design flaw?
Edited by Charlesitis on Monday 14th February 07:43
Edited by Charlesitis on Monday 14th February 07:43
I originally read that and thought, nah, you'd be fine...
Then I read:
According to NASA the average person needs 0.84 kg of O2 per day. For a person at rest 0.617 kg per day. Body tissues need 14.7 L of Oxygen/hour
According to PSU Homepage | Penn State University the lowest % Volume of O2 a person can survive at standard pressure is about 17.5%. Considering you would sleep for 8 hours you will need 117.6L of O2.
How long would it take to use up just the O2 in 1 m3 for life?
The volume in Litre (L) in cubic metre (m3)is: 1000L/m3. 21 % of the atmosphere consists of O2 by volume. So, 1000 L of air consists of 0.21 x 1000 L = 210 L of O2. If 17.5% of the atmosphere consists of O2 by volume, then 1000L of air would consist of 0.175 x 1000 L = 175 L of O2.
Usable Oxygen is therefore 210 L - 175 L = 35 L (0.051kg) for a person.
So a airtight room 12 ft wide x 12 ft long x 8 ft ceiling (3.6 m x 3.6 m x 2.4 m = 31.1m3) will have enough O2 for 1.9 days (according to NASA).
So yes, two people immediately puts it down to less than a day and the car is a much smaller space.
I'm shocked that they couldn't beat their way out, Shirley the doortop frames are not strong enough to withhold someone bracing and pushing from inside, but heyho!!
Then I read:
According to NASA the average person needs 0.84 kg of O2 per day. For a person at rest 0.617 kg per day. Body tissues need 14.7 L of Oxygen/hour
According to PSU Homepage | Penn State University the lowest % Volume of O2 a person can survive at standard pressure is about 17.5%. Considering you would sleep for 8 hours you will need 117.6L of O2.
How long would it take to use up just the O2 in 1 m3 for life?
The volume in Litre (L) in cubic metre (m3)is: 1000L/m3. 21 % of the atmosphere consists of O2 by volume. So, 1000 L of air consists of 0.21 x 1000 L = 210 L of O2. If 17.5% of the atmosphere consists of O2 by volume, then 1000L of air would consist of 0.175 x 1000 L = 175 L of O2.
Usable Oxygen is therefore 210 L - 175 L = 35 L (0.051kg) for a person.
So a airtight room 12 ft wide x 12 ft long x 8 ft ceiling (3.6 m x 3.6 m x 2.4 m = 31.1m3) will have enough O2 for 1.9 days (according to NASA).
So yes, two people immediately puts it down to less than a day and the car is a much smaller space.
I'm shocked that they couldn't beat their way out, Shirley the doortop frames are not strong enough to withhold someone bracing and pushing from inside, but heyho!!
Is the vent intake (recirculate flap) closing on engine shutdown a normal thing? Friend has a BMW and said it happens with his, a few minutes after the engine is shut down the vent intakes close, sealing off the cabin. What is the reason for this and isn't it a safety hazard in situations such as this?
How would they have unlocked the car to get in it in the first place if they didn’t have the fob?
unless they unlocked the car, put the keys down, got in, and then how would it have locked again? Keyless cars lock if the key is going out of range, but if they had unlocked it put it down and then got in the car how could it be out of range?
I’ve never been in a car that locks when you shut the door, everyone with auto locking does it as you drive off over a certain speed
unless they unlocked the car, put the keys down, got in, and then how would it have locked again? Keyless cars lock if the key is going out of range, but if they had unlocked it put it down and then got in the car how could it be out of range?
I’ve never been in a car that locks when you shut the door, everyone with auto locking does it as you drive off over a certain speed
A very methodical man had just shy of 13 hours to attempt to roll the door lock switch? Also, how did they get in the car without the fob? My Mazda 6 locks the doors automatically if you unlock it and walk off. If they were going out, did neither have a mobile phone? I know they're in their 60's but you'd have thought one would've had a phone for emergencies!
Earthdweller said:
cmvtec said:
I don't suppose a couple in their 60s have the combined strength to force their way out.
What they didn't do is unlock the car from the inside...
Deadlocks ? What they didn't do is unlock the car from the inside...
My son locked me in our car, stood outside laughing and I couldn’t open the doors from inside
I have accidentally deadlocked people inside a car at a petrol station as muscle memory had me double-clicking the lock button every time I walked away!
donkmeister said:
Earthdweller said:
cmvtec said:
I don't suppose a couple in their 60s have the combined strength to force their way out.
What they didn't do is unlock the car from the inside...
Deadlocks ? What they didn't do is unlock the car from the inside...
My son locked me in our car, stood outside laughing and I couldn’t open the doors from inside
I have accidentally deadlocked people inside a car at a petrol station as muscle memory had me double-clicking the lock button every time I walked away!
stupidoldget said:
“Once I found out how simple it was to unlock, I kicked myself that I did not find this way out… I had this mind-set that I did not have the transponder so I could not get out.”
MattyD803 said:
waynecyclist said:
Could be an urban myth but I am sure that I have read somewhere that is what they are designed for.
Yes, myth or not, I'm pretty sure this is a tried and tested way of breaking a window......(assuming your car has removable headrests!) 
I'm not convinced that ANY cars are completely sealed to the extent that they become 'air tight', even if they have a flap in the intake.
Bare in mind that the ventilation system (when not in recirc mode) operates on a 'supply only' basis, the air change is facilitated (or balanced) by virtue of having a series of vents (usually towards the rear of the car), which allows the 'over pressure' to be expelled to atmosphere. From my experience, these are normally integrated into the monocoque, behind bumpers or floor panels, typically allowing air to be pulled through the cabin when in motion due to the low pressure area void formed behind the car.
Then, on top of this, you obviously have various rubber seals, wiring grommets, gaskets and joints, which will allow infiltration.
A closed box, sure. It wouldn't be pleasant, but airtight enough to cause 2 people to suffocate? I don't think so.....although being trapped in such a situation in hot weather/direct sunlight would be a very different situation.
Bare in mind that the ventilation system (when not in recirc mode) operates on a 'supply only' basis, the air change is facilitated (or balanced) by virtue of having a series of vents (usually towards the rear of the car), which allows the 'over pressure' to be expelled to atmosphere. From my experience, these are normally integrated into the monocoque, behind bumpers or floor panels, typically allowing air to be pulled through the cabin when in motion due to the low pressure area void formed behind the car.
Then, on top of this, you obviously have various rubber seals, wiring grommets, gaskets and joints, which will allow infiltration.
A closed box, sure. It wouldn't be pleasant, but airtight enough to cause 2 people to suffocate? I don't think so.....although being trapped in such a situation in hot weather/direct sunlight would be a very different situation.
The flap by the filter on Mazda's shuts to recirc mode (to keep rodents out most likely) when you power it off.
Saying that the door handles will still work the same from the drivers side so why he didn't just use it like a normal car is beyond me, should have his drivers licence taken away at the very least.
Saying that the door handles will still work the same from the drivers side so why he didn't just use it like a normal car is beyond me, should have his drivers licence taken away at the very least.
untakenname said:
The flap by the filter on Mazda's shuts to recirc mode (to keep rodents out most likely) when you power it off.
Saying that the door handles will still work the same from the drivers side so why he didn't just use it like a normal car is beyond me, should have his drivers licence taken away at the very least.
Makes sense. Is there a way to manually open the flap when the engine is off, or is it operated by the engine running? Saying that the door handles will still work the same from the drivers side so why he didn't just use it like a normal car is beyond me, should have his drivers licence taken away at the very least.
Gassing Station | General Gassing | Top of Page | What's New | My Stuff