LPT: Using the recirculating button the right way in your vehicle.

  1. One other time to recirculate the air is when you want to avoid stinking smell outside, example passing through Milpitas, CA

  2. Yes! Mine is always set on recirculate thanks to my commute right past a meat rendering plant. A k.a. "The Stink Factory"

  3. I see a small, black-looking carcass on the side of the road and you better believe I'm scrambling for the recirculate button. Once skunk odor gets in your car you don't get to forget it for a few minutes.

  4. My car has a fresh air sensor and when there are fumes coming in (stuck in traffic) automatically switches the recirculation ON.

  5. At first I thought you were simply stating that this idea was also shared on that website. But no it’s literally plagiarized lol.

  6. It is also just completely incorrect. It's akin to recommending putting a window air conditioner in the middle of a room for peak efficiency.

  7. Particularly relevant when traveling through long tunnels. All the air there is basically fumes, fumes, fumes. Windows up, recirc on.

  8. Even if you don’t smell the fumes, you should have recirculate on when you’re in traffic. The amount of particulate junk in traffic is horrendous because it hasn’t had a chance to dissipate yet.

  9. The new Mercedes S-Class has a fart ventilation in the seat, so the driver can gas out in peace without anybody noticing

  10. You want to draw outside air into the car in the winter because it's drier. Unless you run the AC in the winter too (a good way to unfog windows btw), recirculating cabin air will fog up all your windows thanks to the humidity in your breath.

  11. You won't be. With the temperature setting dialed up, heating that fresh air doesn't cost you anything, as it uses heat from the engine.

  12. Cause the cold never bothered me anyways. Seriously though, I love the cold, loved having windows open in Germany/UK, which is why I’m so miserable in Hell (FL) 🥵🫠😵

  13. I thought that using the recirc also dehumidfies the interior air (which might be a GOOD THING in the cold (so as to clear interior misting of the glass parts)

  14. I was using recirculate in the winter and it took way too long for me to figure out that that was the reason why it was almost impossible to get the windshield defogged.

  15. So, it's complicated. Air coming out of the ac is at 100% humidity because it's cooled to dew point and then condensates. It's now much cooler than the surrounding air, but as soon as it mixes with surrounding air, the cold air warms and humidity goes down. Each time this cycle happens more humidity is removed from your car or home. So recirculation does reduce humidity.

  16. If you live north of the 49th parallel, you learn pretty quickly to turn off recirculation in the winter. The increased humidity will fog up your windows, fast.

  17. Just turn the ac button on. It won't actuality cool the air if you have your heat on. It acts like a dehumidifier in the winter

  18. I live north of the 60th parallel, and I've used the recirculation to get the cabin warm faster in the winter. When fog started appearing at the A-pillars I turned it off. When it disappeared I turned it on again. I kept repeating the procedure until the cabin was warm.

  19. I always used recirculation until I got a portable CO2 monitor during the pandemic. It's shocking how quickly CO2 rises in the car and how it drops to normal almost immediately when you open a window.

  20. A car is not that air tight my guy. You might have an exhaust leak that’s going into your cabin.

  21. I suspected this on long road trips. I periodically open the windows when I start feeling a little foggy. Glad someone actually tested this out with a sensor. Now I know its not just in my head!

  22. THIS. I also witnessed my car get up to 2500 ppm of CO2 with recirc on in less than 20 minutes. I never use recirc anymore after I learned this.

  23. This is the exact reason why, at least in Europe, air recirculation turns itself off automatically after a while. You will quickly expend the oxygen in the car (especially if you also have passengers) and, with no fresh air coming in to replenish it, it quickly becomes dangerous for the driver.

  24. Tip for BMW owners, our cars (even back to 2006 and maybe earlier) have an automatic recirc. Based on temp/humidity and even some that have sniffers they will turn turn recirc on and off if you just leave it in auto

  25. Remember to turn to fresh occasionally as the carbon dioxide level can build up on recirc. I have noticed that I will get fatigued on the highway and then realise that the air con is on recirc. The minute I turn to fresh or crack a window I feel a lot better.

  26. Yeah I was going to ask, "what is this reused air thing?" If it's not pulled in from the outside... Won't it all become co2? Is it some sort of mix? I'm still a little hazy on how it recirculates air, but not using the outside air...

  27. Besides being able to cool your car down more, recirculating the air does not provide much of a benefit both in terms of fuel efficiency and wear and tear on the AC. The reason for this is how most AC compressors work on most cars. When the AC is on, the compressor will continuously run. How much cooling you get will be determined by how much air is blown through the AC system, and in some cars, how much hot air is mixed in to increase the temperature. That means your AC compressor will run just as hard with a little bit of cooling or with you blasting the AC. The recirculation will only make it easier to cool your car down on a lower air velocity. It will not make it more efficient (in most cars). Electric cars might operate differently.

  28. I don’t think that applies to all cars. The air conditioning compressor in my older Subaru is pretty noisy, and when I have it on recirculate and it isn’t very hot (sub 70°) outside (lots of wildfire smoke where I am rn), I can hear the compressor cycling on and off once every 30 seconds or so, but once it gets above 80° or so it doesn’t cycle off at all.

  29. Op is right about everything but one thing to add, using recirculation will usually turn on the AC compressor, regardless of if you want hot air to come out of the vents! That's a lot of wear and tear on the compressor for no reason, and it makes your hot air cooler! That's why you shouldn't use it in the winter.

  30. In my car, turning on the defrost will kick on the AC compressor (it can then be turned off if I want), but not the recirculation switch by itself.

  31. As someone else said, recirc and the compressor automatically kicks on when you use defrost. Because the seals in the AC system need to be lubed even during the winter. You don't need to leave it on for long, especially since you're wasting extra gas while it's on. But definitely give it 30 seconds to do it's job before you switch it off.

  32. my family and i in singapore always use the recirculation button. waaaaaay too hot outside not to (and yes, breathing in weird smells or carbon monoxide from traffic is horrible!).

  33. For convertible car users (at least my miata), I also use that button to stop the hot air from hitting me. Basically on this car, even when you put the fan to off, the vents are still in the open position and will blow on your face/feet when going fast (as if you turned the fans to at least medium depending on the speed). With this button, it completely closes off the vents and no air comes through! It should be the same air as outside but as it comes through the engine grill it feels hotter than the one hitting me from the side when I have the top down

  34. Also, it's easy to overlook the cabin air filter, which most car manufacturers recommend changing about every 30k miles. That can be part of why many older cars smell musty if it's not changed to a new one, and can reduce your ac performance.

  35. And tunnel fires! Making sure to recirculate the air can make the difference between coming out alive or suffocating inside

  36. If someone farts in the car, you will have to make the judgment call at to which exhaust from which tailpipe you want to be inhaling over and over again.

  37. Why wouldn't you also want to recirculate hot air that's already been warmed by the car's heating system in the winter?

  38. Related note: recirculating in the winter (perhaps you want to recirculate the warm air) will cause a lot of fogging because the air is so humid and the windows so cold.

  39. AS A CANADIAN: Please turn off recirculation in the winter. Humidity builds up inside the car and can stick to the windows and windshield creating ice inside the car that can obstruct your vision which is a serious safety concern!

  40. Bad advice. If you leave recirculating on for only a few minutes when the car is full, you will feel intoxicated and start losing focus because of lack of fresh air. (CO2 Buildup). If the car is not full it will take longer but still for long trips you should always let fresh air in.

  41. I may be wrong but I believe that doctors have come up with a term to describe the harm caused by this scenario. Carpool Tunnel Syndrome.

  42. It is surprising how few people on this thread even mentioned it. Fresh air is way more important than most people think and apparently more important than AC efficiency or smell from traffic.

  43. Our car's always been in recirculation because of the intense heat and pollution outside. Been through very long trips with it on. Doesn't seem to bring that much trouble to us though.

  44. Why is this not the top comment? People need to see this. It's like you are in a crowded schoolroom/office with no open windows. You start losing focus and you get sleepy. Very dangerous for the driver.

  45. If I'm smoking in my vehicle, I turn off recirculated air and turn the fan on high. Then I set it to blow out of both the top and lower vents simultaneously, while closing the vent by my driver window. This forces air to rush past me and up out of the open window. I have smoked in cars for years without there being a noticeable smell because all the smoke goes straight out of the window.

  46. When I smoked cigarettes I'd buy those "smoker's candles" and burn them in the cupholder periodically. Worked wonders.

  47. While we're at it can anyone explain the snowflake icon button? I assume it means AC but it seems like turning the dial to blue should already be turning on AC?

  48. Without the AC on (your snowflake by the sounds of it) the dial only manages how much heat is being pulled off the engine and into your cabin. Full blue will be outside air with no engine heat.

  49. The red/blue thing has a very simple concept. Let's say you don't use recirculation. The fan draws air from outside. If it's on red, it directs the air through a pipe close to the hot engine, and that heats up the air. This sends hot air in the cabin. If you set it to blue, it just sends the air from outside directly in the cabin, without heating it through the engine. The red/blue dial is like a mixer of how much engine air and how much atmosphere air you will get.

  50. Using recirculate and AC together too much can build up moisture in your AC system. The result will be a car that smells like musty gym socks or wet dog.

  51. You could, but you can get fresh outside air that is just as warm with no fuel penalty, since it's warmed using heat from the engine.

  52. Toyota? Unclick the temp from the max a/c position. Now you can turn on/off recirculating manually. Max A/C forces recirculating.

  53. Perhaps you're writing this from a place where winters aren't bitterly cold. If not, why would you turn the recirculation off in the winter? The same principles apply to heating air as cooling it.

  54. Because heat rises and the intake for recirculating is under your seat. It is basically recycling the cold air in your cabin until it’s hot enough to reach the floor and even then it’s not much. In the cold you want to use heat coming out the floor vents and fill up from the bottom as quickly as possible and recirculating at the bottom actually slows this down. There’s a reason the recirculating button is the shape that it is.

  55. If you keep it on in winter with your defroster that's when you'll notice your windows fog back up after a bit.

  56. Another life tip I’ve learned is if you turn off recirculating while going through a drive thru car wash it’ll make your car smell fresh and clean for a few days.

  57. I always have it on all the time as I almost never use it in the winter anyway. And then there's these cars that you have to turn recirculation on each time you turn on the AC, it's fucking stupid and annoying.

  58. THANK YOU! I've been using recirculating most of the time only for the pollutants concern, but I never knew what to do about the baking in the sun.

  59. And a helpful hint for anyone that finds themselves driving on a dusty gravel road make sure to turn recirculate off as having it on draws dust into your car.

  60. I do have it off to get the hot air out of my car like you suggested but other than that it’s always on recirculate, including winter lol

  61. I live on the pacific coast and use recirculation with the a.c. on all year to dry out the air so my car doesn't get moisture inside trapped for the sometimes days it sits.

  62. Some car's recirculating turns on automatically when reversing to avoid ingesting exhaust gases. It should also be turned on in galleries for the same reason

  63. What do I do if I am driving with a passenger on a congested motorway full of fumes; and then my passenger lets out a toxic fart?

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