Second hand weed smoke does not lead to any meaningful increase in THC plasma concentration
Every high school stoner that's hot boxed a car before class with friends knows firsthand that's not an accurate statement.
But smelled in passing outdoors, sure.
Likewise, what is the rate of CO2 production from an average sedentary human?
On top of that, what is the rate of combustion byproduct production from burning plant matter in a closed passenger compartment?