[supertinu]

I think we have too much of contemplation happening on this thread based on the limited data that is available. Neither I think any of the comments are data backed, its more of what we think is the case or what we have heard over time. I am fairly certain that Air Conditioning as a technology does not have a possibility of killing lives due to CO formation, ofcourse there can other causes for CO to creep inside a system but not due to AC cycling.

And yes I am also not a expert on this matter to give conclusive information . Btw I did hear from a ford technician once when i went for my Ikon check up that re-circulation mode is never 100%, it allows atleast 5% fresh air to avoid CO2 formation inside cabin due to extended usage and it kinda made sense to me. Atleast on my Ikon and even on my bro's City I have noticed that even in recirculation mode, some outside odor does creep in though its really mild.

[Santoshbhat]

This thread is quite an eye opener. I must admit I do have a tendency of keeping the AC on re-circ mode 1) For more effective cooling 2) to keep the fumes of the smoke spewing lorry in front, out.

Is this risk also applicable when the car is on the move?

So there's a reason why in some cars like the Laura , the AC/ fan vent starts in fresh intake mode by default every time on start up. I have got into a sort of a ritual of setting it to re-circulation every time I start the car.

This is what the car's manual says :

Recirculated air mode prevents polluted air outside the vehicle from getting into the vehicle, for example when driving through a tunnel or when standing in a traffic jam.

You should not leave recirculated air mode on over a longer period of time, as “stale” air may result in fatigue in the driver and occupants, divert your attention and also cause the windows to mist up. The risk of having an accident increases. Switch recirculated air mode off as soon as the windows begin misting up.

There is no mention of any risk of carbon monoxide poisoning or any warning against use of AC in re-circ mode for too long when stationary.

[sandeepmohan]

I can explain a little only for the car I own which is a Fiat Linea. If you hit the Air Conditioning button directly, the system manages the fresh air, re circulate air flap on its own based on various condition which I do not know. The indication on the climate control shows the car shape with Auto displayed above it. I use the Auto mode mostly. It is only if I notice a lot of dust and smoke outside do I switch to re circulate.

[avinash_clt]

Originally Posted by supertinu

And yes I am also not a expert on this matter to give conclusive information . Btw I did hear from a ford technician once when i went for my Ikon check up that re-circulation mode is never 100%, it allows atleast 5% fresh air to avoid CO2 formation inside cabin due to extended usage and it kinda made sense to me. Atleast on my Ikon and even on my bro's City I have noticed that even in recirculation mode, some outside odor does creep in though its really mild.

Agree with you on this. I've noticed the same on my Laura too. On hard acceleration and braking , i can clearly smell sth burnt, believes its the smell of brake dust (or maybe sth else. i'm not sure), but it occurs even after air-con had been in re-circulation mode for the past 30min or more. It is very mild and goes off quickly.

Originally Posted by Santoshbhat

So there's a reason why in some cars like the Laura , the AC/ fan vent starts in fresh intake mode by default every time on start up. I have got into a sort of a ritual of setting it to re-circulation every time I start the car.

Yes it should be the reason. Same with my Verna and previous i20 (with ACC) also. Each time the air-con is switched off, it automatically enters fresh-air mode (eg: switiching off the air-con while on the move , turning off the vehicle). Its the default setting but we can select the re-circulation mode after turning off also (Eg: switiching off the vehicle in a traffic signal)

I believe even during long highway drives, its enough that every half an hour or so , just use the fresh-air mode for 5min and switch back to the the re-circulation mode. Almost in all the owners manuals sth similar is recommended. Wasn't aware of the same till a couple of years ago and it does make a difference. It is a pain in vehicles like Laura for the air-con to cool by being in fresh-air mode all the time.

[Naturalist]

Adding to this,
there was a news reported last month that a father has locked his 2 years old son in the car with all windows locked when he went to meet some one. He forgot about his son totally. When he came back after 2 hours he found his son dead.

The pity thing is that this happened in a remote village. 2 boys who saw the car shaking and they thought it was a ghost as they could not see this 2 years old boy inside the car. They ran away out of fear.

The Hindu : Cities / Chennai : Child, left behind in locked car, dies

[srishiva]

Originally Posted by Naturalist

Adding to this,


The Hindu : Cities / Chennai : Child, left behind in locked car, dies

Very sad news. Thought could be because of the heat which happens abroad. No details on the air circulation mode etc.

[anoop_lamba]

Whether driver is asleep or awake. Same amount of fumes will be formed inside the car over a period of time if AC is on and the vehicle is at standstill or barely moving.
Does this mean there is a potential danger to health in case we are stuck ina long jam and we have our AC on?

[Honda Monk]

Its common logic I assume that since all the opening are closed how came fresh air (or better say oxygen) will get inside.
The inside blocked air is re-circulated through the a/c grills.
The CO2 content of the inside air keeps increasing with time (due to respiration). After some time this high CO2 content in air makes one feel dizzy then he faints and eventually dies.

[alpha1]

WHY will heating coil produce CO on its own, when I engage the heater circuit on?

[psp62in]

Originally Posted by vina

In recirculation mode, The air from cabin is recirculated inside. There is no source of CO inside the cabin. In fact in the examples he has given, it is more likely that the AC was NOT on recirculation and hence the system pulled in some of the CO from exhaust - all the cases are for vehicles stranded in water.

Agree! There have been many cases all over world, when people have slept in a stationary car in an enclosed space (e.g. A garage) with engine running, and have been found dead - due to CO poisoning. So, in this particular case, if the car was parked in a enclosed area, CO poisoning would be a very good possibility, otherwise the reason of death has to be something else.

Originally Posted by Naturalist

Adding to this, there was a news reported last month that a father has locked his 2 years old son in the car with all windows locked when he went to meet some one. He forgot about his son totally. When he came back after 2 hours he found his son dead

In this case, the unfortunate death may have been due to very high temperature. The temp can rise rapidly in a closed car due to the high glass surface area (green house effect).

[krish82]

Originally Posted by Honda Monk

Its common logic I assume that since all the opening are closed how came fresh air (or better say oxygen) will get inside.
The inside blocked air is re-circulated through the a/c grills.
The CO2 content of the inside air keeps increasing with time (due to respiration). After some time this high CO2 content in air makes one feel dizzy then he faints and eventually dies.

I really cannot digest this fact, In home even split AC's do they have fresh air vents? i guess not, so if four of a family in a small room with window/split AC on, sleeps the whole night, they should be dead by morning due to co2 poisoning.

[Honda Monk]

Originally Posted by krish82

I really cannot digest this fact, In home even split AC's do they have fresh air vents? i guess not, so if four of a family in a small room with window/split AC on, sleeps the whole night, they should be dead by morning due to co2 poisoning.

I think the air volume in car is a fraction of your room's.
Secondly in room one can never perfectly seal it (like it gets in a car by those rubber linings around door) as there are many slits left open especially beneath doors and those slivers.

ELSE PLEASE EXPLAIN HOW CAN ONE GET FRESH OXYGEN IF ALL POSSIBLE WAYS ARE CLOSED.

It would be good to know if there is any other possible thing.

[JediKnight]

CO or carbon monoxide is very toxic. A concentration as low as 1.5% can cause death in a 2-3 minutes.

CO2 or carbon dioxide is not toxic. That is it is not poisonous and you cannot die because inhaled too much C02. If you were put in a air sealed container for a long time you would die. You will die because of asphyxiation since you would slowly consume all the oxygen and convert it to CO2, reaching a state where there is not enough oxygen to sustain life.

It is *VERY BAD* for your health to be in a closed air chamber ( room or car ) with the AC on for long periods. The reason is as follows. The primary trigger for human reflex to detect stale air is triggered via rising air temperature. For example the stuffy feeling you get when there are too many people in a ill ventilated room . But with the AC keeping the air temperature low we do not realise the slowly deteriorating air quality. The reason people do not die while sleeping in rooms with split ACs and all windows/doors closed is that the air sealing is not perfect and the larger air in a room ( as Honda Monk correctly pointed out ). In a car the air sealing is much better and cubic volume much less, hence a much higher risk of asphyxiation. Also in a car which is in less than perfect condition there is chance of fumes from the engine bay making themselves into the cabin. ( via faulty/leaky HVAC plumbing ) Car upholstery is also known to emit fumes. A cheap perfume can also be dangerous.

[mgh]

Originally Posted by Honda Monk

I think the air volume in car is a fraction of your room's.

The fresh air intake in modern cars is just below the windshield (you can see the slots) and strictly from outside. So as long as the stationary car is in the open, and the AC is not in recirculation mode, even with engine running, chances of sufficient carbon monoxide getting in are negligible.

Secondly, even in so called recirculation mode, some amount of fresh air should come in. AC systems design has to provide some amount of fresh air, when air-conditioned space is occupied by people, whichever mode it is in.

Split ACs depend on opening and closing of doors for fresh air. Window ACs had provision for some amount of fresh air. Hardly anybody ever used that.As mentioned by Honda Monk, the volumes of the rooms ensure that carbon dioxide levels remain low enough.

As far as I am concerned, I have travelled in my earlier Indica umpteen times for upto five hours with AC on recirculation, never any problem. But then, 'the low quality' Indian cars have panel gaps, don't close tight etc., so are safer!

I would say that do not close windows in a stationary car, if anybody is inside, whether or not the engine is running. In a bad traffic jam, definitely shut off engine and open windows, if you are stuck at one place for long.
Other than that use AC in the mode, which gives you acceptable FE.

Carbon Monoxide poisoning is insidious. In the old days, we had a charcoal fired water boiler kept in the bath room. Unfortunately, the bath room had a window that for obvious reasons was kept closed. It did not have slats. Result was one day, I came out after a bath, and collapsed. Fortunately, I was unconscious for a very short time. Needless to say the boiler was moved out of the bathroom immediately.

Modern cars have very low carbon monoxide output, so unless gases can leak from engine compartment into the cabin, the chances of carbon monoxide poisoning are low, with engine running in a an open space.

If you have fully electronic door opening and closing, there are chances of you being stuck in a closed car. You need to keep a hammer inside the cabin to smash open a window in emergencies.

[Naturalist]

I do not believe CO has anything to do this. It is definitely due to AC being switched off and there was no air-recirculation. There may be fumes that could have got into the car from the engine bay which might have choked the kid to death with no air recirculation.