I thought that was a feature of many cars sold in Europe starting sometime in the 80’s.
The HEPA filters typically also contain an activated charcoal layer to chemically adsorb the VOCs and gases that remain after the particulate filter.
IT may have started earlier but the first one I can definitvly think of where the sensor is is on the 1999 e-46 (3-series) BMW likes to be the first with many features that today are looked at as 'commom must have items". They do not restrain themselves and let others develope the features first, a very innovative car manufacture.
About “Santa Toys” I was able to keep a very complete set of tools that never touched someting dirty (like an engine or brake or suspension component) strictly reserved for interior trim items. Learning sunroof and convertible top repair without any technical schooling was at best challenging.People don’t realise that you can still be a mechanic and never touch an engine or brake system today. We had a shop foreman who made a darn good living (off of a percentage of our labor) just keeping the special tools board in order.
That could be true. The system(s) I was referring to didn’t sense air quality. They just switched to recirculate anytime the car was stopped or moving very slowly.