[mgh]

1. On a hot day in almost any car, you will find that the AC will not cool, unless it is on recirculation mode.
2. In most cars, the AC will cool properly only with recirculation on.
So there is no choice. If you keep windows partially open, cooling will be affected!
The best way as per me, is to stop about once in two hours, keep doors open, and walk around a bit to stretch your legs. If you can't, open windows partially for a short time, and close them again at intervals of one to two hours.
Running an AC in a parked car with engine running and windows fully closed, is definitely dangerous.

[mac187]

Few things I learnt from this thread.
A. Do not use recirculation (with windows closed) for more than 2 hours at a stretch.
B. Its better to use fresh air on highway runs.
C. Never use A/C when car is stationary either in fresh air or recirculation.

I had know about point C for a while now. A is an eye opener to me. But I too have the same question for point B as Warwithwheels

Originally Posted by Warwithwheels

Just wondering if this reasoning can be extended to Long distances AC buses or any other mode of transport where a large chunk of people are forced into a confined AC cabin for extended period of time (Read:Overnight). Or do they come equipped with the appropriate re-circulation mechanism?

[revintup]

The biggest advantage of re circulating air is that it keeps all the pollution and exhaust fumes outside. More than cooling benefits i think this is the main reason people choose to drive in re circulation mode.

But got to admit, my Honda salesman advised to drive always in the fresh air mode during his demo.

Wish there was a proper filtering mechanism to keep the pollutants out. Guess some of the more expensive cars have it.

[srishiva]

If you have good filters, you should never use recirculation. A little bit of smell is not that bad.
I hope the ACC does not malfunction and set the recirculation mode ON permanently !

[lancer_rit]

Originally Posted by mgh

1. On a hot day in almost any car, you will find that the AC will not cool, unless it is on recirculation mode.

Depends on the car and also whether there are decent sunfilms to reduce heat absorption. Many cars cool fine in fresh air mode. In any case, one could switch to fresh air within a few minutes.

2. In most cars, the AC will cool properly only with recirculation on.
So there is no choice. If you keep windows partially open, cooling will be affected!

All cars I drove a lot, cool fine with fresh air mode on. So, please don't generalize so simply.

As smartcat posted earlier, whenever on a long drive, AC must be in fresh air mode as CO2 builds up with time (depending also on the #occupants in the car). That makes everyone drowsy with time w/o necessarily realizing why - the driver may just doze off at the wheel due to too much CO2 and you can imagine the consequences...
CO2 danger isn't as sensational as CO danger, but it can happen much more easily and frequently... Drive safe.

[mgh]

I am talking of the smaller cars, where the AC compressors, as mentioned often on Team-BHP are deliberately underpowered for better FE.
And, if you want to be absolutely safe, do not use AC

[Mpower]

Is there a post mortem report that has been released?

[vb-saan]

I remember reading about a couple of such incidents here in Singapore a few years back.

Here is the wiki link on CO poisoning.
Carbon monoxide poisoning - Wikipedia, the free encyclopedia

And another link on one such case: 5 teens dead from car carbon monoxide poisoning in Florida motel room | Mail Online

[vina]

Originally Posted by GTO

My first guess was that the drunk cop choked on his own vomit. Nope, it's not as rare a cause of death as you think : Rockstars who choked on their own vomit

Thank you for posting those links, Warwithwheels! I have to admit to sleeping in the car sometimes, with the air-con on, and didn't have the slightest clue of potential danger. NEVER ever again. Check this post by Navingulia:

Navingulia's post is misleading (CO can and will kill, but AC has nothing to do with that) and simply wrong on some counts.

For example, CO molecular weight is 28 (12 for C and 16 or O) which is almost exactly the same as that for on air (air is roughly 29 - N2 which is 3/4 of air is exactly 28, O2 which is most of the rest is 32. Most of the rest is actually lighter than N2). Technically 29 is more than 28 - but anybody who knows these things will tell you this isn't enough difference to cause CO to "escape" - it takes thousands of feet of altitude before you get low-O2 in the air problem and O2 is 32 (vs. 29 of air). The car's height is not enough to have enough vertical column that can fight off diffusion.

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.


If police doesn't suspect foul play - you should suspect that they are at the very best being callous and shirking work (and embarrassment at being clueless).


Blaming CO sounds sciency and sexy, but CO may not always be the culprit, in fact I would find the vomit theory more plausible than the CO theory.

Other possibilities like drug/alcohol overdose and similar factors are also plausible - policemen across the world are not above these things, and they would rather not admit to it (assuming they know this is the cause in the first place) when a cop is involved.

[vnabhi]

I always drive in fresh-air mode on highways, and shift to re-circulate mode while passing through human habitation to avoid stench of cattle, etc. I've mentioned this in some of my travelogues too.

But in the city, i do the opposite. I switch to fresh air mode for a minute whenever i see a free, unpolluted stretch, or once every 15 minutes. The AC in re-circulate mode in the Fiesta is a chiller, and it gets too cold after a while. Fresh air sets this problem aright.

I also noticed that keeping the AC in re-circulate mode for long in the Fiesta makes me feel a wee bit suffocated.

[ghodlur]

Originally Posted by vnabhi

But in the city, i do the opposite. I switch to fresh air mode for a minute whenever i see a free, unpolluted stretch, or once every 15 minutes.
Where would you get that stretch without the stench, that too in city.

The AC in re-circulate mode in the Fiesta is a chiller, and it gets too cold after a while. Fresh air sets this problem aright.

This is applicable maybe only during winters, in Summers you do need the coldness continously and recirculation is the best bet for that. I normally drive with AC in recirculation mode all the times (not for long stretches) after seeing the amount of black smoke being spewed out by the ST buses, trucks and the BPO pickups.

[vnabhi]

Originally Posted by ghodlur

This is applicable maybe only during winters, in Summers you do need the coldness continously and recirculation is the best bet for that. I normally drive with AC in recirculation mode all the times (not for long stretches) after seeing the amount of black smoke being spewed out by the ST buses, trucks and the BPO pickups.

You do have a point---i was referring to highways that are relatively empty, like the one towards Bangalore/ Nagpur and Mumbai from Hyd.

In Hyd city , we do get relatively free stretches in Jubilee Hills and KBR park area.

[nitinbose]

Originally Posted by Warwithwheels

Just wondering if this reasoning can be extended to Long distances AC buses or any other mode of transport where a large chunk of people are forced into a confined AC cabin for extended period of time (Read:Overnight). Or do they come equipped with the appropriate re-circulation mechanism?

Such buses never travel at a single stretch. They often stop to pickup and drop passengers, breaks etc., so the cabin air is refreshed.

[krish82]

I actually never use the air intake mode in my AC. Reasons:
1. I feel more pollution comes into cabin, which does not go out easily.
2. The AC filter will get clogged if this mode is used frequently.
3. Cooling becomes less effective.

But this i am following for last several years. May be some particular car models have a problem in their AC design set up, which when stationary emits Carbon monoxide.
May not be a fair comparison, But what about aircrafts, we sleep in it for hours with all passengers producing Co2, does it have Fresh air intake mode too?

[nozzlering]

Air Conditioner has nothing to do with CO. All the package air conditioners in the world work on same principle. If ac emitted CO, or any poisonous gas, people would have been dying in buildings, theatres, buses, trains..
As supported earlier in the thread, the gas has to do with the engine exhaust.
Most probably, the car was parked in an enclosed space, where, after few hours, lack of oxygen led to generation of CO which could have killed the cop.

I feel ac can never cause death by any toxic gas generation. But the engine can. If the car is in open space with good supply of fresh air, engine wont emit any toxic gas.