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Old 16th October 2007, 16:38   #1
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Default A/C: internal circulation leads to stale air?

In many other threads, i have seen people advising to keep the A/C in internal circulation mode.

However, i have a (dumb ?) question about the same: by keeping 'internal circulation' active, especially with 4/5 people in the car, will it not lead to stale air being circulated after a short time?

Even the santro manual recommends keeping the air at 'external' and moving it to 'internal circulation' only when there is an irritating smell outside.


Please clarify.
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Old 16th October 2007, 17:56   #2
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Quote:
Originally Posted by sreenidhibr View Post

by keeping 'internal circulation' active, especially with 4/5 people in the car, will it not lead to stale air being circulated after a short time?

Even the santro manual recommends keeping the air at 'external' and moving it to 'internal circulation' only when there is an irritating smell outside.

that's right. switch to "recycling" air mode when driving through dust, or for quicker cooling. else, it's the "fresh" air mode for that 'fresh' feel inside the car
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Old 18th October 2007, 01:29   #3
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Correct sreenidhibr,

Thats why in a lot of offices etc they try to have some sort of air cycling system vs a split AC, since recycling the air causes co2 (?) levels to go up and after some time that causes drowsiness.

cya
R
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Old 18th October 2007, 09:49   #4
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perfect. right.

but, what would one do while 90% driving is in thick smokey traffic-laden roads like Andheri(e)-Ghatkopar and the Sion-panvel highway? have to go on recirculation mode most of the time.

- use a good deo on yourself, keep yourself clean
- never give a ride to a colleague who smells like a goat
- dont eat inside your car.
- use a good freshener - preferably of the citrous kind

i have followed this strictly and i'm on AC 100% - all the time, and am sure my car smells cleaner that keukenhof gardens. LOL

Last edited by gbpscars : 18th October 2007 at 09:51.
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Old 18th October 2007, 09:53   #5
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Of course, external circulation is supposed to be better. But more often than not, it is accompanied by lots of dust and pollution. Of course you get fresh air but also get dust and pollution, which by themselves are allergens and cause some damage. Better to get your fresh air in the morning than on our dusty roads. All manuals say this, but then which manufacturer prepares a manual specific for Indian urban and rural dustlands.
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Old 18th October 2007, 10:41   #6
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Usual home air conditioners also inject fresh air into the room, whether they are window mounted or split systems.

Car is a different story and I don't think in recycle mode they use any outside air. As per drive.com.au, some high end cars automatically switch to fresh air mode after couple of hours.


So if you're driving for longer time like 70-80 minutes alone of say over 30-45 minutes in packed car, it may be worthwhile to occasionally let some fresh air in.


More CO2 will lead to headaches / feeling unwell.
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Old 18th October 2007, 10:44   #7
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In external circulation mode, don't the cars have some sort of an air filter which absorbs odors and dust while sucking in fresh air into the passenger compartment?
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Old 18th October 2007, 11:01   #8
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Different cars have different quality air filters. Most do not filter the outside air and recirculation is the only saviour (atleast in Indian cities)
If you have more people inside the car, switch to external air quite often.
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Old 18th October 2007, 11:15   #9
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Quote:
Originally Posted by gbpscars View Post
- use a good deo on yourself, keep yourself clean
- never give a ride to a colleague who smells like a goat
- dont eat inside your car.
- use a good freshener - preferably of the citrous kind

i have followed this strictly and i'm on AC 100% - all the time, and am sure my car smells cleaner that keukenhof gardens. LOL
gbpscars, you've missed the point. You are only addressing the issue of SMELL. How about oxygen content? After prolonged periods the inside air is rich in carbon dioxide and low on oxygen.

Quote:
Originally Posted by megger View Post
Usual home air conditioners also inject fresh air into the room, whether they are window mounted or split systems.
Not so, megger.
Window units have a lever operated small flap to allow some outside air to be mixed.
Split systems do not have any means to take in outside air.
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Old 18th October 2007, 11:18   #10
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Quote:
Originally Posted by anupmathur View Post
gbpscars, you've missed the point. You are only addressing the issue of SMELL. How about oxygen content? After prolonged periods the inside air is rich in carbon dioxide and low on oxygen.
oh yes. i have missed it.
sorry.

thanks for reminding, i've forgotten oxygen after i came to mumbai
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Old 18th October 2007, 11:35   #11
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I keep wishing for the "recirculate" button on my steering wheel :-) because I use it more often than any other button on the dash.

A lot depends on the quality of the air filter - which are pretty decent in cars that are 10lak+. A good air filter does a decent job even in Indian conditions. A good pollen filter is a must in cities like Bangalore. I mostly keep fresh air mode unless I am going behind those autos/trucks that use coal for fuel - or those serene open drainage things.

Stale air is without sufficient oxygen - which is a definite no. Outside air maybe bad but I am sure it is not worse than stale air. Do not underestimate our body's capacity to deal with general pollutants. But it definitely can't deal with air that lacks oxygen - results in fatigue, headache and even death. The headache you get with your windows down is not due to air pollution, but noise pollution.

I say if it is clear enough (without smoke), it is clean enough. Don't use those deo/air-freshener thing, it's just hiding the stink - by adding more dangerous chemicals!

Last edited by androdev : 18th October 2007 at 11:38.
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Old 18th October 2007, 14:23   #12
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I always used to use my car AC in fresh air mode till I came to Hyderabad. I mostly use it in 'recirculate' mode in the city, as the outside air is filthier. But if the drive is for periods more than 30 mins, then I switch for 'fresh air' mode for a couple of minutes. I use the recirculate option more often, as the cooling is better and faster.
On highway drives however, I use both options 50:50.

Last edited by vnabhi : 18th October 2007 at 14:24. Reason: forgot a 0
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Old 18th October 2007, 14:37   #13
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Quote:
Originally Posted by gbpscars View Post
, i've forgotten oxygen after i came to mumbai
__________________________________
LOL!!
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Old 18th October 2007, 15:15   #14
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I have seen that in indica, if AC is switched off and only blower is on, even on internal circulation mode, you can get whif of outside air(eg diesel smoke from trucks if you pass one).
This lessens with AC on, but still it looks as if its not complete recirculation.
Maybe with the push button internal/external HVAC things are different, but in case of manual switch one(found in older models without heater) internal is not completely internal.
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Old 18th October 2007, 15:28   #15
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i ve got a corolla and noticed some fumes kinda smell when its on the fresh air mode. does the air come from the enginebay?
i just open the windows for a few mins if the outsides arent too smokey .
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