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Dangerous Recirculate Air Design Choice

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#24 ·
WJBertrand said:
The recirculate mode is not 100% exclusion of outside air. There’s still a significant percentage of fresh air blended in, even when in that mode. This has always been the case.
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This.
Its always been 20% fresh air in the past, pretty sure there's a federal rule requiring that. Some Toyota systems have included a "filter" mode with a 3 min time limit which actually does cut off outside air, but "recirc" does not and never has. If someone wants to fiddle with an OBD2 link there's a couple available settings relating to auto mode.
 
#25 ·
CoffeeBear said:
doing some googling I guess there is some concern where a lot of people in the car at once could cause a build up of CO2 but I question if the the overall system is airtight enough for that to be a concern. I've never noticed any ill effects driving 3-4 hours with my whole family in the rav4 or my past cars in the summer with recirc on the whole time.
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People breath out CO2 not CO. Totally safe vs. deadly unsafe.
 
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#29 ·
Well, the best way to help cool your vehicle off quickly, besides going through the nearest car wash, is to first use the windshield washers. Doing this, not only cools off the extremely hot windshield, but helps to cool the air inside the vehicle. You also want to have the A/C on fresh air. This will suck out the hot air inside of the car and replace that air with outside air that is already cooler. Once the vehicle has started to cool off, you will want to switch over to recirculate mode, because this mode is the most efficient cooling mode once the air has started to cool off. Another reason for switching to recirculate mode is that when you are stuck in city traffic, you do not want to be breathing in the other vehicles carbon monoxide. If you can smell the rotten egg smell of the vehicle ahead of you or the diesel fumes, then it is definitely time to switch. If you are on the Interstate highway or country roads, then fresh air is the way to go. Have a great day :)
 
#31 ·
I usually drive in "Eco" mode. That means the car starts the AC also in "Eco" mode and with "recirculation" enabled, each time I start the car. I don't really bother with manually switching it out of "recirculation" mode because I haven't noticed any subjective temperature advantages in doing that after few tries. As for air quality, according to my portable air quality sensor (I got it to measure particulate concentration because I was curious how good the stock cabin air filter is at removing that, but it can also measure CO2), the CO2 concentration inside the car never reached "unhealthy" levels no matter for how long the "recirculation" mode was on and no matter how many passengers I had in it. So the car is never "air tight" (for as long as the AC/fan is running), regardless if "recirculation" mode is enabled or disabled. This is just an easily verifiable fact, not someone's random assumptions.

As for "unpleasant smell" - I do have some of it when starting the AC after the car was unused for 12+ hours and if the previous day was very humid, but that's probably just a residual smell of some mold forming on evaporator (I guess Toyota is one of those manufacturers that still can't figure out how to properly design evaporators for very humid climate) and since it quickly goes away (regardless if "recirculation" is on or off) it doesn't really bother me.
 
#32 ·
Omgwtfbbq said:
I usually drive in "Eco" mode. That means the car starts the AC also in "Eco" mode and with "recirculation" enabled, each time I start the car. I don't really bother with manually switching it out of "recirculation" mode because I haven't noticed any subjective temperature advantages in doing that after few tries. As for air quality, according to my portable air quality sensor (I got it to measure particulate concentration because I was curious how good the stock cabin air filter is at removing that, but it can also measure CO2), the CO2 concentration inside the car never reached "unhealthy" levels no matter for how long the "recirculation" mode was on and no matter how many passengers I had in it. So the car is never "air tight" (for as long as the AC/fan is running), regardless if "recirculation" mode is enabled or disabled. This is just an easily verifiable fact, not someone's random assumptions. As for "unpleasant smell" - I do have some of it when starting the AC after the car was unused for 12+ hours and if the previous day was very humid, but that's probably just a residual smell of some mold forming on evaporator (I guess Toyota is one of those manufacturers that still can't figure out how to properly design evaporators for very humid climate) and since it quickly goes away (regardless if "recirculation" is on or off) it doesn't really bother me.
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Mold forming in the evaporator? Doesn’t sound healthy to me.
 
#34 ·
Colonel said:
Dangerous? Absolutely not. Not to your liking? Sure.

Fix?

Hit the button when you turn on HVAC...then enjoy a donut!

I don't like the SFlow. But a simple button press makes the problem go away.
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well then, he wouldn't have anything to complain about
SaratogaSam said:
When the gas engine is running, cutting off outside air increases the possibility that the air in the car will have high carbon monoxide levels.
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#36 ·
For what it's worth (this thread is kind of all over the place), the manual says:
Outside/recirculated air mode may automatically switch depending on the temperature setting or the inside temperature.

Before reading that, I was convinced that my 2021 SE had some sort of timer or other mechanism that would not allow the system to stay in Recirculate after a certain length of time (like, 5 minutes or so). I would "shut the vents" and at some later point notice that the system was back in Outside air mode. I had a Sprinter-based RV that did the same thing.
 
#37 ·
Every car I've ever driven automatically turns on recirculate if A/C was left on (and is therefore on when the car started).

The fumes you noticed were probably from being near dirty-burning diesels, because there's still like 10% outside air coming into the car. It just happened to be that you noticed when you weren't near those vehicles anymore, and when you turned it off, you were getting clean air.

I usually have the opposite problem in my gen 3, where I turn off recirculate, get behind a dirty burning vehicle, and wish I had it on. Haven't noticed any issues with my gen 5 that I don't turn off recirculate on.

Even if what I'm saying doesn't apply you aren't going to be smelling much from a newer rav4, the engines are very clean burning, and CO itself is oderless.

Buy a battery powered CO alarm if you're that worried.
 
#40 ·
Neiman said:
Mold forming in the evaporator? Doesn’t sound healthy to me.
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This has been a known/ongoing issue for over a decade: Toyota A/C smells Fix is rather simple:
1. Use outside air mode just before you park (the 5th generation RAV automatically does this for you).
2. Get a charcoal cabin air filter.
 
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