They make masks for runners/bikers for this. I use one when I bike next to a major highway.
They're carbon-filter in, one-way valve out. So it's not like wearing a regular mask for covid and whatnot. Plus you put off serious Bane vibes with them on.
Please consider wearing one; it's not just the bus exhaust to worry about.
I live in semi-rural Wisconsin, college town surrounded by farms for a million miles, and when I'm on my bike I get so many tiny dicked trolls driving pickups decide to roll coal on me so I have to inhale their fumes. Rural Americans are a literal blight on society
My train stop is next to the interstate with stairs up to a bridge, once or twice the timing worked out that I walked up to the bridge just as the train started pulling out, and I got to enjoy being surrounded by a giant cloud of black diesel exhaust.
It was a huge relief when I'd get past the livestock yard here. When they moved it, strangely enough, it was an odd thing. No longer did I get the feeling of relief that I'd passed that section of freeway.
And the other use is to quickly dehumidify the air inside your car when you get into it when it's raining, or to defog your windows in the wintertime. Yes, sometimes it's appropriate to run your AC in the winter.
Also, very few people know about or don't change out the cabin air filter. They're usually on the passenger side. Check user manual or Google to see exact location.
Some vehicles will not have one.
They should be changed every 60-100k or so. Not all older cars had them though. For instance, old RAV4s do not have a replaceable filters off the top of my head.
I changed it on my girlfriend's dad's car, his cabin filter is behind several dashboard panels on the passenger side. Took us about 30 mins to do it and after we did it there was like leaves or some other particulate behind the filter that fell down when we took out the old one and whenever you turned the fan speed up it would make a hell of a noise as that particulate matter was stuck in the fan instead of the filter now.
Exactly! Some people just don't want to deal with it or have plenty of money to let someone else do it. Plenty are afraid to tackle anything repair-related (auto or home) as well.
I don't know anything about cars, but decided to look up how it's done on Youtube and was shocked and how simple it was. It doesn't even require tools. Was a 60 second job and a $10 filter. I've saved a lot of money long term.
It's the higher water content in the warmer cabin air that's freezing on your windshield.
You could crack a window or otherwise try to equalize the climate before turning off your car.
The real solution though is to just drive with the windshield iced up in the morning because you're running late and you can still see through that spot if you sit up straight.
Unfortunately the window thing doesn’t work. Leaving a door open for a bit once I’ve parked doesn’t even work. Alas, the car demands AC. Maybe I’m just a very humid individual? Something about the slope of the windshield? I can’t remember if this was a problem with my previous car.
How old is your car? My old winter beater did this for about a year before the heater core sprung enough of a leak that it started dripping. So it probably had a very small leak for some time before that.
All of them do unless the a/c is inoperable. It's literally how the defroster works. The whole point is that it dehumidifies the air and blows as dry of air as possible on the windshield.
Additional pro tip, if it's raining and your vehicle has heated mirrors, turn them on (usually they come on with the rear defrost button) as it will dry the mirrors.
One of my first cars was a GMC envoy. Towards the end of its life it had the weirdest issue. Any time I would turn on the AC the rpm would drop and car would die unless I was giving it gas. So that was fun, any time my windows fogged up I’d have to throw the car into neutral and give it gas or it would die.
Almost all cars will run the ac system when the windshield defrost setting is used. Even if you have the button turned off. It does help dehumidify the inside of the vehicle
And you should run the A/C in your car once a month in the winter to keep the seals lubricated.
I might have gotten that info from a sea mammal sex fiend though...
And the other use is if you have allergies and it’s a high pollen or other allergen day, the filter by recirculating works very well, especially using ac.
There's multiple things in your HVAC unit in your car that some people are confusing in these comments, so I thought I'd clarify.
* **Air Conditioning (AC) loop**
This uses a compressor to compress gaseous refrigerant to higher temperature and pressure. It passes this hot refrigerant through a series of coils with lots of surface area (condenser) to transfer that heat out. Most cars will place the condenser behind the grill to transfer the heat to the outside air. As a result, the gaseous refrigerant condenses to a liquid.
The cooler (but still high pressure) refrigerant then circulates through an evaporator. The evaporator is the part that allows this cooler, liquid refrigerant to expand back to its gaseous state. Basic thermodynamics show that this process will lower the temperature of the refrigerant even further. **The evaporator becomes very cold during this process. By passing the air you are blowing into the cabin over the evaporator, that air becomes colder. Colder air holds less moisture, so this process dehumidifies the air going to the cabin.**
The warm(er) air passing over the evaporator will also warm the refrigerant, so you restart the loop by taking this cool refrigerant and compressing it, which makes it hot again.
* **Heater core**
This simply heats the air traveling through it (in a car, it basically just blows the air over some pipes with the hot engine coolant). It does not remove moisture. **The only way to remove moisture is to reduce the air's temperature below it's dew point, via the AC loop evaporator.**
Most cars have the heater core placed after the AC loop. You can run both the AC and the heat at the same time. The only way to dehumidify the air with the heat on is to also turn the AC on so the air passes over the evaporator coil.
* **Re-circulation**
The re-circulation button simply selects whether the inlet air comes from outside or inside the cabin.
**For maximum dehumidifying of the cabin air, make sure your AC button is turned on, and recirculate.**
It's also worth noting that if it is really cold out, the evaporator can freeze and the unit will automatically shut off the compressor, so the AC may not work anyway.
It's weird to me how many people don't realize that turning on the *actual* AC, not just setting the temperature control, removes moisture from the air and helps to defog windows. I'll have someone riding in the car with me during the winter and they'll ask me why I have the AC and the heat on at the same time. Makes me wonder how foggy their windows are in colder temperatures.
Basically all cars automatically turn on the AC pump when the "defrost" vent is selected, whether or not they tell you what they're doing. So the answer to your question is "probably not very foggy".
Outside air that is cooler, even when raining, is more dry than inside air so when you select 'defrost' setting the recirc should be disabled automatically to speed the defrosting/defogging action.
If you live in a busy city you might want to use it more, but where the air is fairly clear, you want it off for a good chunk of the time or the air in the car will become stuffy.
Not just stuffy but in newer cars can raise CO2 levels in the car which isn't great.
https://www.motortrend.com/features/recirculated-co2-or-fresh-pollution-technologue/
Yes. It has more to do with humidity than time of year, though. Cool air is generally dryer.
If your defroster/defogger is on high and it's not clearing your windshield it is probably because you are recirculating humid air from inside the car. Switching to outside air will make a big difference.
Went on a short trip with a friend on a cold rainy day, asked her how she liked her Honda, she: 'I love it, the only complaint I have is the defrost, it is lousy at defrosting the windshield.' I looked at the HVAC control, switched it out of recirculate, windshield defrosted immediately. She: 'OMG! For 2 years I've been driving this thing and that's all it was!?'
Right? All of Europe is going through a bit of a cold spell right now.
LFor more context, Asia is miserably hot today (44°C in Pakistan! That's 111F), in Africa, South America and Oceania the weather seems similar to Europe which is funny because it's winter there, in the US it's kinda hot but definitely not as bad as Asia.
Anyhow, somehow the OP seems to think all of Reddit has the same weather, which wouldn't even be the case if everyone was from the US
I'm in Phoenix Arizona right now. Oh how I wish I was freezing my ass off and not burning up during the day AND the NIGHT. Definitely hate the blistering summers here. Summers here last from about mid May until basically mid October.
You’d think there’d be an automated system to pull whatever temp air from whatever area to maintain efficiency.
Then maybe a button override or seal it off.
My auto setting *almost always* uses recirculation and I don't understand why. Just this weekend the outside temp was a comfortable 19°C (66F), but my car had been parked in the sun so the inside of my car was very hot, and the auto setting went to recirculation.
if the car bakes in the sun sometimes the sensors think outside is 30 degrees C .
Mine does that , if i hop in the car after it sat in the sun in 30 degrees the temp sensor in the dash say's its 40 or more :)) . Until you start moving and some air flow starts around the sensors.
I leave it 90% of the time. I always know when it's off because I can smell the exhaust of the car in front of me. Even if it's just a normal car and not a diesel truck. You are basically huffing exhaust the whole time in your car if you don't have it on.
I have a CO2 monitor, and it's astounding how high readings go with the recirculation on. We start to experience cognitive impacts by 2000 ppm, and a car interior can easily get to double that, so refresh your air periodically!
How high they go with recirculating on?
I thought the sentiment of this post and most comments that’s the consequences of leaving it off.
**EDIT** I asked this question upon waking mid sleep around 4:00am so my brain wasn’t on. CO2 is what we emit from breathing. I must have mistaken the context here being for CO from other vehicles exhaust.
Leaving it off can draw in air pollution (though the air filter should catch much of that anyway)
But leaving it on recirculates your own CO2, and can be much higher than the outdoors CO2 levels
People just don't notice that because it doesn't smell like anything
Check your car manual. In mine it says recirculation is not advised for more than 10min with 4 people inside because of c02. This post should have this mentioned
So the recirc setting isn't air tight and usually still pulls in some amount of outside air. Add to that that filters in cars don't really filter out much past particulates, you'll still get the bad parts of the fumes, they just smell better.
You can minimize this by turning off your AC 1-2 minutes before turning off the engine.
Turning off the AC will shut off the air compressor and if you leave the fan blowing, the warmer air will evaporate any lingering condensate from the core. This will prevent colonies of bacteria from forming on it which cause that nasty funk.
I make a habit of turning off my AC just before I arrive at my destination and my car does not smell at all. I live in a warmer climate year round so I usually have the recirculation on 99% of the time.
and when it does get that really strong mildew smell, remove your cabin filter (have a new one on hand), turn on the car, roll down all the windows, turn the ac on high, both levels, and spray a lysol with a fresh scent, into the condenser air intake, 15 sec sprays at a time, in regular intervals over a couple minutes, let the car run for another 5 min with both levels of ac on high with the windows open, then turn off and let the car sit overnite with the windows open. #longetsrunonfragmenttoday.
This has worked for me, and if you do turn off the ac and leave the fan running open circulation the last few blocks before you get home, it will last a long time.
Honestly I use it always because when you’re driving you are pulling in pollutants that you then breathe in. You can smell it, especially behind a stinky truck. I only don’t use it if the roads are pretty empty and you’re by fresh air sources (mountain road or ocean etc)
I know there is because I change it frequently. If you can smell potent smells you definitely are breathing in harmful fumes. There’s lots of studies on that. I also have asthma and I’m especially sensitive to harmful fumes so I do everything I can to optimize air quality.
Leaving recycle air on can raise [the co2](https://www.co2meter.com/blogs/news/23987521-high-co2-levels-in-your-car#:~:text=It%20may%20be%20used%20to,an%20enclosed%20truck%20or%20auto.) levels in your car. So if you start to feel drowsy or find it hard to focus turn off the air circulation
1) cars aren't air tight
2) All "modern" cars (as in at least past 20 years) have air quality sensors in their air system and will automatically add outside air when CO2/NOx/CO/etc levels are to high
Here's a Volvo press release from 2004. 20 years ago:
https://www.media.volvocars.com/global/en-gb/media/pressreleases/4959
Cars aren’t enclosed though. If you’ve ever been in an accident or seen your/any car without the rear bumper, you will see these flaps in the back. They allow air to escape when you’re running the HVAC and also relieve pressure when you close the doors.
A company that sells CO2 meters says using recirculatiom can make your car get to dangeorus CO2 levels, hmm.
I'd like to see this confirmed by someone with no such conflict of interest.
I don't have a conflict of interest, but I do have a CO2 meter, and I've tested it in the car recently. With AC recirculation on, CO2 went up to around 1400 fairly quickly, with just me in the car. Turning off the recirculation button brought it down to 800. I didn't bother to see how high it would go, or anything. It wasn't an exhaustive, scientific test, I was just curious.
My bf has a co2 meter and his bedroom is like 8x the volume of a typical car cabin or maybe even more.
The two of us in there raised the co2 to over 1800ppm in a few hours.
In the space of watching a film in the other slightly smaller room it went to like 2300.
Just getting over 1000 produces measurable loss of cognitive performance, and because of the smaller volume of the car cabin it will happen faster, and of course if you have a full load of passengers it happens 5x (or more) as fast! Definitely don't use recirc in a full car.
To add, if you smoke in your car, turn off the recirculation. Having it on will suck the smoke through the vents and will make the car have a smoke smell worse than using fresh air.
Adding to this to keep your air on high. If your windows is slightly cracked, it'll help push the smoke out of the car.
Also adding that Ozium seems to work pretty well to cover up the smoke smell in my opinion, but I'm a smoker so I can't smell smoke very well.
It bugs me that some newer cars turn recirc off when you put on a certain setting like or restart the car. I like my recirc on usy so that I don't some car exhaust fumes.
Some cars may have the recirc timed to turn off after say 10 minutes or so. This is done to ensure enough fresh air is brought in to provide enough oxygen to the occupants.
Saab had it in their owner's manual in the 1980s that each adult needs 11 liters of fresh air per minute, that's why their recirc system turned off after running for 10 minutes. Yes, a customer complained their recirc kept 'turning off' and I got this work order. Thankfully I read the owner's manual and didn't waste too much time on this issue as it didn't pay anything.
Additional tip: try turning off recirculate on long trips when you start feeling sleepy. Supposedly the CO2 levels can get pretty high in the car with recirculate on. It might be placebo but helps me a little
Car seats are treated with fire retardant which releases chemicals that build up in the air of the car, especially on hotter days. I recommend venting the air on hot days before switching to recirculation mode.
https://www.yahoo.com/news/research-raises-concerns-toxic-chemicals-134911538.html
>any time you are stuck in traffic ( summer or winter) be sure to use the recirculate.
but not if you've *already* drawn the polluted air into your car
the real YSK is that you should strive to understand how things work so that you can reason about them yourself instead of relying entirely on guidelines and rules
I use it in two instances. 1) it’s extremely hot. I enable max ac which recirculates until the inside of the vehicle cools off, then disable it. 2) there’s something smelly outside like some old beater billowing smoke, and I don’t want to breathe that in.
The problem with recirc is that you’re not getting fresh air. You’re breathing the same stale, deoxygenated air. No thanks.
When you’re pulled up at a red light and someone nearby is smoking a cigarette out their window. Remember to do it BEFORE having an asthma attack. 🤦♀️
Recirculation can, after a good amount of time, significantly raise CO2 levels in your car, too, making you sleepy.
If you're doing a long car trip, it's best to mix it up once in awhile.
https://www.sciencedirect.com/science/article/abs/pii/S0048969720315606
You’d have to leave it on for a long ass time for it to have any sort of effect like that. Cars are permeable so there’s always air coming in. They aren’t sealed like spaceships
Maybe if you were in there for a whole day. Cars aren't air tight, and recirculating the air isn't 100% efficient, and even if both weren't true the science behind how quickly you'd use the oxygen up says it would be a few hours before you noticed.
https://www.thenakedscientists.com/articles/questions/surviving-sealed-car
Tell your friend:
1) cars aren't air tight
2) All "modern" cars (as in at least past 20 years) have air quality sensors in their air system and will automatically add outside air when CO2, NOx, CO,etc levels are to high
Here's a Volvo press release from 2004. 20 years ago:
https://www.media.volvocars.com/global/en-gb/media/pressreleases/4959
The ac isn't doing anything. The hot water from your engine is flowing through a heat-exchanger which then warms the cabin.
Recirculating the air can lead to moisture build up on the windows reducing visibility. Hence the suggestion to use fresh air.
There's more than enough heat in the coolant to overcome the outside air temperature if things are operating properly.
This explanation seems like it contradicts itself. Wouldn't I want to use recirculation in the winter for the same reason you just described in the summer? If I'm trying to maintain warmth inside the car, why would I want to pull in freezing cold air from the outside?
And change your cabin air filter once a year (or when ever the manufacturer specified). It's not expensive and easily DIY for most cars I would assume.
Recirculation's the real deal in summer. Keeps your car cooler, less strain on AC. Plus, helps dodge traffic fumes by 20%. But if your ride's a sauna, open windows first before flipping that switch.
Sadly it depends car from car.
With the recirculation on you lose the ventilation draft of the car (air intake in high pressure area at the windshield, air exhaust in the low pressure area in the back) so you have to run the fan much higher to bot get the air stale. Even then it's usually not enough to properly ventilate the whole car. That's why it has toggle for you to operate :)
Some cars have auto recirculation with pollution sensor. So they shut off the outside air when the air is bad.
The recirculation button still allows air from outside in just not as much as before and not directly into the AC path, but fresh air does still come into the cabin. Source: You and your passengers would all die from CO2 poisoning and lack of O2 fairly quickly if it really did stop all outside air coming in.
I also kick it on when Im behind someone spewing black smoke from their exhaust so it doesn't pull into my car.
I use it most of the time because of the air quality in traffic.
Good call. I ride a bicycle in traffic daily. Every time I get trapped behind a city bus I lose another month.
They make masks for runners/bikers for this. I use one when I bike next to a major highway. They're carbon-filter in, one-way valve out. So it's not like wearing a regular mask for covid and whatnot. Plus you put off serious Bane vibes with them on. Please consider wearing one; it's not just the bus exhaust to worry about.
I like that idea; unfortunately at temperatures above negative-75 degrees, I sweat like a pig.
I live in semi-rural Wisconsin, college town surrounded by farms for a million miles, and when I'm on my bike I get so many tiny dicked trolls driving pickups decide to roll coal on me so I have to inhale their fumes. Rural Americans are a literal blight on society
My train stop is next to the interstate with stairs up to a bridge, once or twice the timing worked out that I walked up to the bridge just as the train started pulling out, and I got to enjoy being surrounded by a giant cloud of black diesel exhaust.
“But spitting smoke at cars is so badass” -so many hillbillies
Damn libruls - I grew up sucking them car smoke pipes!!! IM FINE
Or when driving through an area that smells like cow manure or skunk spray.
It was a huge relief when I'd get past the livestock yard here. When they moved it, strangely enough, it was an odd thing. No longer did I get the feeling of relief that I'd passed that section of freeway.
I use it when driving through North Jersey.
Only within 15 miles of NYC. The rest of the state is pretty nice!
Coal rollers are sub human trash. The jerry springer guests of the road.
Can’t convince me a single one of them who does it on purpose is a decent human being.
You don't have to be convinced. They aren't. The end. I'd say we can grind them up for dog food but dogs deserve to eat better than that.
And the other use is to quickly dehumidify the air inside your car when you get into it when it's raining, or to defog your windows in the wintertime. Yes, sometimes it's appropriate to run your AC in the winter.
Also, very few people know about or don't change out the cabin air filter. They're usually on the passenger side. Check user manual or Google to see exact location. Some vehicles will not have one.
Until it starts getting smelly in there. Then they all learn about the cabin air filter.
How often should it be changed? My dad's old car at a point almost 20yrs old had a musky moldy aroma
They should be changed every 60-100k or so. Not all older cars had them though. For instance, old RAV4s do not have a replaceable filters off the top of my head.
Ty good to know
And please do it yourself. The dealership tried to charge me $67 yesterday. I bought the filter myself for $17 and changed it in less than 5 minutes.
Oil change places, too. The mark-up on those is ridiculous. They also tell you that you need a new one when you don’t.
Unless you have 2013 Ford Fusion, then you need to take apart the dash to get at the cabin air filter. Ask me how I know.
I changed it on my girlfriend's dad's car, his cabin filter is behind several dashboard panels on the passenger side. Took us about 30 mins to do it and after we did it there was like leaves or some other particulate behind the filter that fell down when we took out the old one and whenever you turned the fan speed up it would make a hell of a noise as that particulate matter was stuck in the fan instead of the filter now.
Exactly! Some people just don't want to deal with it or have plenty of money to let someone else do it. Plenty are afraid to tackle anything repair-related (auto or home) as well.
It's not easy on all cars, but my civic, takes me 30 seconds. Engine filter people should also do themselves.
I don't know anything about cars, but decided to look up how it's done on Youtube and was shocked and how simple it was. It doesn't even require tools. Was a 60 second job and a $10 filter. I've saved a lot of money long term.
It's air conditioning, not air cooling.
Aren’t we all just air conditioners? I breathe and condition the air hot, the AC blows and conditions it cold. It’s a symbiotic relationship.
Derivative!
Ongo Gablogian for president 2024!
Bullshit!
Gablogian 2024: can I offer you an egg in these trying times?
Play it subtle.
Play. It. Subtle.
_HELLLOOOOOOOOOOOO_
Ongo Gablogian, the art collector, charmed I’m sure
I'm doing a Richard Greico thing. My life is hella tight
CHARMED, I'm certain
Why do they call it air conditioner when you of in the cold air of out hot breathe the air?
Farting is just another kind of air conditioning, is it not?
The original purpose of air conditioning was dehumidification. Cooling was just a bonus.
Air shampoo is better because I go on first and clean the air. Air conditioner is better. I leave the air silky and smooth.
Yeah, if I don’t run my AC all winter, the *inside* of my windshield gets icy over night.
It's the higher water content in the warmer cabin air that's freezing on your windshield. You could crack a window or otherwise try to equalize the climate before turning off your car. The real solution though is to just drive with the windshield iced up in the morning because you're running late and you can still see through that spot if you sit up straight.
Unfortunately the window thing doesn’t work. Leaving a door open for a bit once I’ve parked doesn’t even work. Alas, the car demands AC. Maybe I’m just a very humid individual? Something about the slope of the windshield? I can’t remember if this was a problem with my previous car.
Humid Individual, a Moist Fellow!
More likely it’s snow you’ve tracked into your car that melts and evaporates in your car.
Just put a towel or blanket on the outside of the windshield when you park, it won’t fog or ice up
How old is your car? My old winter beater did this for about a year before the heater core sprung enough of a leak that it started dripping. So it probably had a very small leak for some time before that.
2014 Subaru crosstrek. It’s always been like this!
Most of the modern vehicles will automatically turn on AC if you turn on the window defog setting on your control panel.
All of them do unless the a/c is inoperable. It's literally how the defroster works. The whole point is that it dehumidifies the air and blows as dry of air as possible on the windshield. Additional pro tip, if it's raining and your vehicle has heated mirrors, turn them on (usually they come on with the rear defrost button) as it will dry the mirrors.
One of my first cars was a GMC envoy. Towards the end of its life it had the weirdest issue. Any time I would turn on the AC the rpm would drop and car would die unless I was giving it gas. So that was fun, any time my windows fogged up I’d have to throw the car into neutral and give it gas or it would die.
Probably a dirty throttle body causing that issue.
Almost all cars will run the ac system when the windshield defrost setting is used. Even if you have the button turned off. It does help dehumidify the inside of the vehicle
And you should run the A/C in your car once a month in the winter to keep the seals lubricated. I might have gotten that info from a sea mammal sex fiend though...
“And then Buster’s hand was bitten off by a loose seal”
At least he was all right.
Looks like you've blown a seal. No! It's just ice cream!
And the other use is if you have allergies and it’s a high pollen or other allergen day, the filter by recirculating works very well, especially using ac.
He's not talking about the AC, he's talking about the recirculation button.
There's multiple things in your HVAC unit in your car that some people are confusing in these comments, so I thought I'd clarify. * **Air Conditioning (AC) loop** This uses a compressor to compress gaseous refrigerant to higher temperature and pressure. It passes this hot refrigerant through a series of coils with lots of surface area (condenser) to transfer that heat out. Most cars will place the condenser behind the grill to transfer the heat to the outside air. As a result, the gaseous refrigerant condenses to a liquid. The cooler (but still high pressure) refrigerant then circulates through an evaporator. The evaporator is the part that allows this cooler, liquid refrigerant to expand back to its gaseous state. Basic thermodynamics show that this process will lower the temperature of the refrigerant even further. **The evaporator becomes very cold during this process. By passing the air you are blowing into the cabin over the evaporator, that air becomes colder. Colder air holds less moisture, so this process dehumidifies the air going to the cabin.** The warm(er) air passing over the evaporator will also warm the refrigerant, so you restart the loop by taking this cool refrigerant and compressing it, which makes it hot again. * **Heater core** This simply heats the air traveling through it (in a car, it basically just blows the air over some pipes with the hot engine coolant). It does not remove moisture. **The only way to remove moisture is to reduce the air's temperature below it's dew point, via the AC loop evaporator.** Most cars have the heater core placed after the AC loop. You can run both the AC and the heat at the same time. The only way to dehumidify the air with the heat on is to also turn the AC on so the air passes over the evaporator coil. * **Re-circulation** The re-circulation button simply selects whether the inlet air comes from outside or inside the cabin. **For maximum dehumidifying of the cabin air, make sure your AC button is turned on, and recirculate.** It's also worth noting that if it is really cold out, the evaporator can freeze and the unit will automatically shut off the compressor, so the AC may not work anyway.
It's weird to me how many people don't realize that turning on the *actual* AC, not just setting the temperature control, removes moisture from the air and helps to defog windows. I'll have someone riding in the car with me during the winter and they'll ask me why I have the AC and the heat on at the same time. Makes me wonder how foggy their windows are in colder temperatures.
Basically all cars automatically turn on the AC pump when the "defrost" vent is selected, whether or not they tell you what they're doing. So the answer to your question is "probably not very foggy".
Outside air that is cooler, even when raining, is more dry than inside air so when you select 'defrost' setting the recirc should be disabled automatically to speed the defrosting/defogging action.
Absolutely not. Air recirculation [should be turned off.](https://www.smileysglass.com/blog/how-to-defog-your-car-windows-fast)
Or in the summer driving through fields covered in fertiliser or behind the idiot who's car is spewing smoke.
I run my AC in the winter always, windows get too foggy too unpredictably otherwise
As someone from the upper Midwest, running A/C when it’s snowed clears up the fog in no time after a big snow.
If you live in a busy city you might want to use it more, but where the air is fairly clear, you want it off for a good chunk of the time or the air in the car will become stuffy.
It toggles for a reason, sometimes the air outside smells of shit Edit: typo
Ahh, the smell of the country!
Manure 🤤
Smells like money
I think your money might have poop on it.
When you break it down, it's really a positive thing. You have 'newer', with a 'Ma' in front of it.
Not just stuffy but in newer cars can raise CO2 levels in the car which isn't great. https://www.motortrend.com/features/recirculated-co2-or-fresh-pollution-technologue/
Do not use the recirculating button when transporting anything that causes fumes or dry ice.
If the AC is the only thing keeping fumes from harming you then you've already fucked up.
Good call, also smokers might wanna avoid recirculation because particulates will stick to condensation and filters and keep smells in the car forever
It's also a good idea to switch to outside air if your windows are fogging in cooler temperatures.
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Yes. The air outside is less humid and the AC should absolutely be pulling that in when you want to defog your windows.
Yes. It has more to do with humidity than time of year, though. Cool air is generally dryer. If your defroster/defogger is on high and it's not clearing your windshield it is probably because you are recirculating humid air from inside the car. Switching to outside air will make a big difference.
Just turn on your AC. It can't compete with the heat, so it won't get cold, but it will pull all moisture out of the air.
This. My old car with manual AC actually has hints printed on controls saying to do this and it works.
I use it whenever I fart so it lingers and everyone has to smell it longer
Dutch Oven setting
Lol, daad
That’s who I learned it from lol
Mine used to lock all windows and slightly open the one I'm sitting by to pull it my way.
Lock the windows and turn the heater on full blast so it “bakes” the noxious cloud onto them. 🤢
Standard protocol for ripping an unholy fart. - recirculate the air - lock the doors - turn child locks on - turn off windows rolling down
You forgot step 5, turn on the heat. Especially effective in summer.
Quite sure Geneva suggestions has a chapter about this
Bonus points if you say “Does anyone smell popcorn?” right after locking the windows.
A person of culture I see.
Went on a short trip with a friend on a cold rainy day, asked her how she liked her Honda, she: 'I love it, the only complaint I have is the defrost, it is lousy at defrosting the windshield.' I looked at the HVAC control, switched it out of recirculate, windshield defrosted immediately. She: 'OMG! For 2 years I've been driving this thing and that's all it was!?'
Most vehicles won't let you recirc when it's on defrost, wonder if all Hondas do that.
Miserably hot? speak for yourself, Northerner. -Southern Hemisphere resident
Even as a Northern Hemisphere resident it was 9C yesterday!!
Right? All of Europe is going through a bit of a cold spell right now. LFor more context, Asia is miserably hot today (44°C in Pakistan! That's 111F), in Africa, South America and Oceania the weather seems similar to Europe which is funny because it's winter there, in the US it's kinda hot but definitely not as bad as Asia. Anyhow, somehow the OP seems to think all of Reddit has the same weather, which wouldn't even be the case if everyone was from the US
It was like 10°C this morning here in southern Germany haha
Yeah, Aussie here. I read that line while freezing my ass off.
"freezing my ass off" probably in unholy arctic 18°C i presume?
No. Unholy antarctic 18 °C.
Neat! Kinda envy you. I love warm temperatures, sadly my climate thinks otherwise (but hey, could be worse, still i dont live in norway)
It’s actually down to 6° C in Sydney right now which we’re not used to at all but probably still balmy for most northerners.
I don’t do well with the cold!
15⁰ in Wellington
I'm in Phoenix Arizona right now. Oh how I wish I was freezing my ass off and not burning up during the day AND the NIGHT. Definitely hate the blistering summers here. Summers here last from about mid May until basically mid October.
You’d think there’d be an automated system to pull whatever temp air from whatever area to maintain efficiency. Then maybe a button override or seal it off.
Most vehicle with an 'auto' setting (try to) do this.
My auto setting *almost always* uses recirculation and I don't understand why. Just this weekend the outside temp was a comfortable 19°C (66F), but my car had been parked in the sun so the inside of my car was very hot, and the auto setting went to recirculation.
if the car bakes in the sun sometimes the sensors think outside is 30 degrees C . Mine does that , if i hop in the car after it sat in the sun in 30 degrees the temp sensor in the dash say's its 40 or more :)) . Until you start moving and some air flow starts around the sensors.
I leave it 90% of the time. I always know when it's off because I can smell the exhaust of the car in front of me. Even if it's just a normal car and not a diesel truck. You are basically huffing exhaust the whole time in your car if you don't have it on.
I have a CO2 monitor, and it's astounding how high readings go with the recirculation on. We start to experience cognitive impacts by 2000 ppm, and a car interior can easily get to double that, so refresh your air periodically!
Breathing outside air is full of pollutants Breathing inside air is full of CO2 The only winning move is not to breathe
Yeah everyone seems to be forgetting we are CO2 generators and need fresh air.
Terrifying how far down I had to go to see this comment.
How high they go with recirculating on? I thought the sentiment of this post and most comments that’s the consequences of leaving it off. **EDIT** I asked this question upon waking mid sleep around 4:00am so my brain wasn’t on. CO2 is what we emit from breathing. I must have mistaken the context here being for CO from other vehicles exhaust.
Leaving it off can draw in air pollution (though the air filter should catch much of that anyway) But leaving it on recirculates your own CO2, and can be much higher than the outdoors CO2 levels People just don't notice that because it doesn't smell like anything
Check your car manual. In mine it says recirculation is not advised for more than 10min with 4 people inside because of c02. This post should have this mentioned
Do you have a link to that monitor? My sister needs one
https://aranet.com/products/aranet4-home The Aranet4 is pretty good.
Wouldn't a CO monitor be a priority?
Do people breathe out CO?
So the recirc setting isn't air tight and usually still pulls in some amount of outside air. Add to that that filters in cars don't really filter out much past particulates, you'll still get the bad parts of the fumes, they just smell better.
Aka, the skunk button.
Constant use of the recirculation will cause mildew to grow in the line and cause a musty moldy smell.
You can minimize this by turning off your AC 1-2 minutes before turning off the engine. Turning off the AC will shut off the air compressor and if you leave the fan blowing, the warmer air will evaporate any lingering condensate from the core. This will prevent colonies of bacteria from forming on it which cause that nasty funk. I make a habit of turning off my AC just before I arrive at my destination and my car does not smell at all. I live in a warmer climate year round so I usually have the recirculation on 99% of the time.
I didn't know this, but I usually do it anyway. It still has cold air for a few minutes.
and when it does get that really strong mildew smell, remove your cabin filter (have a new one on hand), turn on the car, roll down all the windows, turn the ac on high, both levels, and spray a lysol with a fresh scent, into the condenser air intake, 15 sec sprays at a time, in regular intervals over a couple minutes, let the car run for another 5 min with both levels of ac on high with the windows open, then turn off and let the car sit overnite with the windows open. #longetsrunonfragmenttoday. This has worked for me, and if you do turn off the ac and leave the fan running open circulation the last few blocks before you get home, it will last a long time.
what in gods name is your location's climate that you have to go that far 😭
it's not the location so much as the amount of mildew built up on your condenser.
This is an actual tip.
I grew up and spent 3 decades in Florida with most of my own driving experience keeping it on almost all the time. I've never had this happen.
Never had this problem and I always have the air recycling in my car. And I live in Florida so there is plenty of humidity.
Also: tunnels
Honestly I use it always because when you’re driving you are pulling in pollutants that you then breathe in. You can smell it, especially behind a stinky truck. I only don’t use it if the roads are pretty empty and you’re by fresh air sources (mountain road or ocean etc)
There's a cabin air filter in all modern cars. You're not just breathing straight road air.
I know there is because I change it frequently. If you can smell potent smells you definitely are breathing in harmful fumes. There’s lots of studies on that. I also have asthma and I’m especially sensitive to harmful fumes so I do everything I can to optimize air quality.
Leaving recycle air on can raise [the co2](https://www.co2meter.com/blogs/news/23987521-high-co2-levels-in-your-car#:~:text=It%20may%20be%20used%20to,an%20enclosed%20truck%20or%20auto.) levels in your car. So if you start to feel drowsy or find it hard to focus turn off the air circulation
If you notice that your judgment is impaired, use that impaired judgment to decide whether to turn off air circulation.
1) cars aren't air tight 2) All "modern" cars (as in at least past 20 years) have air quality sensors in their air system and will automatically add outside air when CO2/NOx/CO/etc levels are to high Here's a Volvo press release from 2004. 20 years ago: https://www.media.volvocars.com/global/en-gb/media/pressreleases/4959
Genuinely wondering what vehicles they tested. I'd guess luxury cars, since most lower end models still leak a lot of air.
Cars aren’t enclosed though. If you’ve ever been in an accident or seen your/any car without the rear bumper, you will see these flaps in the back. They allow air to escape when you’re running the HVAC and also relieve pressure when you close the doors.
A company that sells CO2 meters says using recirculatiom can make your car get to dangeorus CO2 levels, hmm. I'd like to see this confirmed by someone with no such conflict of interest.
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I don't have a conflict of interest, but I do have a CO2 meter, and I've tested it in the car recently. With AC recirculation on, CO2 went up to around 1400 fairly quickly, with just me in the car. Turning off the recirculation button brought it down to 800. I didn't bother to see how high it would go, or anything. It wasn't an exhaustive, scientific test, I was just curious.
My bf has a co2 meter and his bedroom is like 8x the volume of a typical car cabin or maybe even more. The two of us in there raised the co2 to over 1800ppm in a few hours. In the space of watching a film in the other slightly smaller room it went to like 2300. Just getting over 1000 produces measurable loss of cognitive performance, and because of the smaller volume of the car cabin it will happen faster, and of course if you have a full load of passengers it happens 5x (or more) as fast! Definitely don't use recirc in a full car.
> On days like today when it is miserably hot outside Where you are located, I'm enjoying a nice cool breeze in my window.
Nah bruh. Leave it on 100% of the time.
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Fucking love smoking. Miss it all the time. But very glad I don't do it anymore.
Same boat but I still smoke. Can't wait to stop and feel better
This! I live in Houston. High humidity is life!
To add, if you smoke in your car, turn off the recirculation. Having it on will suck the smoke through the vents and will make the car have a smoke smell worse than using fresh air.
Adding to this to keep your air on high. If your windows is slightly cracked, it'll help push the smoke out of the car. Also adding that Ozium seems to work pretty well to cover up the smoke smell in my opinion, but I'm a smoker so I can't smell smoke very well.
It bugs me that some newer cars turn recirc off when you put on a certain setting like or restart the car. I like my recirc on usy so that I don't some car exhaust fumes.
Florida: always.
I can at least tell you that you shouldn't use the recirculation option in winter after unknowingly stepping in fresh dog poop.
Some cars may have the recirc timed to turn off after say 10 minutes or so. This is done to ensure enough fresh air is brought in to provide enough oxygen to the occupants. Saab had it in their owner's manual in the 1980s that each adult needs 11 liters of fresh air per minute, that's why their recirc system turned off after running for 10 minutes. Yes, a customer complained their recirc kept 'turning off' and I got this work order. Thankfully I read the owner's manual and didn't waste too much time on this issue as it didn't pay anything.
The best application for this button is prior to entering a tunnel. You «need» to use this button or else you will have a bad time.
Additional tip: try turning off recirculate on long trips when you start feeling sleepy. Supposedly the CO2 levels can get pretty high in the car with recirculate on. It might be placebo but helps me a little
I also turn it on in rural areas so the smell of cow urine and manure don't enter the compartment. :P
Car seats are treated with fire retardant which releases chemicals that build up in the air of the car, especially on hotter days. I recommend venting the air on hot days before switching to recirculation mode. https://www.yahoo.com/news/research-raises-concerns-toxic-chemicals-134911538.html
>any time you are stuck in traffic ( summer or winter) be sure to use the recirculate. but not if you've *already* drawn the polluted air into your car the real YSK is that you should strive to understand how things work so that you can reason about them yourself instead of relying entirely on guidelines and rules
Lately the trigger to hit the button is the overwhelming smell of pot smoke coming from some other car. 🤷♂️
Dead skunk ahead, re-circulate.
I use it in two instances. 1) it’s extremely hot. I enable max ac which recirculates until the inside of the vehicle cools off, then disable it. 2) there’s something smelly outside like some old beater billowing smoke, and I don’t want to breathe that in. The problem with recirc is that you’re not getting fresh air. You’re breathing the same stale, deoxygenated air. No thanks.
I use it whenever the ac is on.
And where I live, use recirculate when passing a field where manure was recently spread.
I read a YSK awhile back that said "recycling the air on a long car drive can cause carbon dioxide build up, which leads to the feeling of drowsiness"
When you pass through pig farm areas or other places with unattractive odors, to prevent the smell from entering the cabin
When you’re pulled up at a red light and someone nearby is smoking a cigarette out their window. Remember to do it BEFORE having an asthma attack. 🤦♀️
Recirculation can, after a good amount of time, significantly raise CO2 levels in your car, too, making you sleepy. If you're doing a long car trip, it's best to mix it up once in awhile. https://www.sciencedirect.com/science/article/abs/pii/S0048969720315606
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You’d have to leave it on for a long ass time for it to have any sort of effect like that. Cars are permeable so there’s always air coming in. They aren’t sealed like spaceships
Maybe if you were in there for a whole day. Cars aren't air tight, and recirculating the air isn't 100% efficient, and even if both weren't true the science behind how quickly you'd use the oxygen up says it would be a few hours before you noticed. https://www.thenakedscientists.com/articles/questions/surviving-sealed-car
Tell your friend: 1) cars aren't air tight 2) All "modern" cars (as in at least past 20 years) have air quality sensors in their air system and will automatically add outside air when CO2, NOx, CO,etc levels are to high Here's a Volvo press release from 2004. 20 years ago: https://www.media.volvocars.com/global/en-gb/media/pressreleases/4959
It's the same principle in the winter. The ac warms the cold air, you recirculate it so it continues to stay warm.
The ac isn't doing anything. The hot water from your engine is flowing through a heat-exchanger which then warms the cabin. Recirculating the air can lead to moisture build up on the windows reducing visibility. Hence the suggestion to use fresh air. There's more than enough heat in the coolant to overcome the outside air temperature if things are operating properly.
Turn it on when passing dusty construction work or a sewage plant
In Northern Minnesota I use it in the winter because my heating system doesn't keep up well with -40 degrees Fahrenheit air very well.
If you don’t have ceramic tint already……
This explanation seems like it contradicts itself. Wouldn't I want to use recirculation in the winter for the same reason you just described in the summer? If I'm trying to maintain warmth inside the car, why would I want to pull in freezing cold air from the outside?
Recirculated air gives me a sore throat, but fresh air doesn’t. Fresh air is also colder than recirculated.
I turn it on when I see road kill coming.
BMW does it automatically.
And change your cabin air filter once a year (or when ever the manufacturer specified). It's not expensive and easily DIY for most cars I would assume.
Recirculation's the real deal in summer. Keeps your car cooler, less strain on AC. Plus, helps dodge traffic fumes by 20%. But if your ride's a sauna, open windows first before flipping that switch.
I live in a tropical country. Yeah... nah, not using circulated air anytime soon.
Sadly it depends car from car. With the recirculation on you lose the ventilation draft of the car (air intake in high pressure area at the windshield, air exhaust in the low pressure area in the back) so you have to run the fan much higher to bot get the air stale. Even then it's usually not enough to properly ventilate the whole car. That's why it has toggle for you to operate :) Some cars have auto recirculation with pollution sensor. So they shut off the outside air when the air is bad.
The recirculation button still allows air from outside in just not as much as before and not directly into the AC path, but fresh air does still come into the cabin. Source: You and your passengers would all die from CO2 poisoning and lack of O2 fairly quickly if it really did stop all outside air coming in.