HVAC airflow (fresh/recirc) & cabin filter

[Zathras]

At some point in time I think I remember reading that on the S550, the airflow path bypasses the cabin air filter when the climate system is in recirculate mode. So there is no filtration unless it's set to fresh air intake. But I could be imagining or misremembering that. Does anyone know for sure?

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[ORRadtech]

I can't confirm that. But since one side of the cabin filter, and there is only one, is open to the exterior common sense would indicate that it is true.

 

[SnowFox]

I've never known (or tryed to know) where the air comes from.

I just pretend it's magic.

 

[GTP]

Just speculating here.

But it could be that Recirc is not fully closed, i.e. that there is always some outside fresh air coming in. I like recirc in the city bc of bad urban air, and recirc off for long trips, just in case that helps keep me more alert. Furthermore, I should think that even recirc air started as fresh.

It's even possible that there is a federal regulation that requires some fresh air mixed with recirc.

 

[ORRadtech]

Just speculating here.

But it could be that Recirc is not fully closed, i.e. that there is always some outside fresh air coming in. I like recirc in the city bc of bad urban air, and recirc off for long trips, just in case that helps keep me more alert. Furthermore, I should think that even recirc air started as fresh.

It's even possible that there is a federal regulation that requires some fresh air mixed with recirc.

Even if that's the case, and I guess it could be, only the air coming in from outside would be filtered. Any recirculated cabin air would bypass the filter.
You also have to figure that any air in the car, before it was started, is unfiltered outside air. Simply opening and closing our big ass doors removes and replaces a pretty significant amount of cabin air volume.

 

[Torched10]

I use recirculation when it's really hot or cold out
It just reirculated air inside car and dirdnt bring on any outside air so there's no point in cabin filter being on play

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