All Cascadias I drive bring bad smells from outside into cab

I have asked a couple of mechanics about this but they do not know what I am talking about so I hope to have some luck on this site. I have driven four different Cascadias from years 2011 through 2015, and ALL of them have done this so I know it is not just my truck. If there is smoke outside from a fire (like when farmers burn their land), or if there is an old truck in front of me that smokes every time it accelerates uphill, or if there is a bad sewer smell in west memphis, the bad smell blows right through into my cab through the HVAC vents. YES, I ALWAYS LEAVE THE A/C OR HEATER ON AIR CIRCULATION MODE which is supposed to prevent outside air from blowing in. I know that the defroster automatically uses the mode which brings air from outside so I try not to use it much.

When I drive my car, I could be behind a car with so much smoke that I cannot see, and I can have my A/C going full blast and I cannot smell a thing. However with all of the cascadias I have driven, I can sometimes even taste the bad smell as it blows right into my face. I turn off the HVAC to prevent further abuse but I have to have it blown in my face first before I can react. Usually when I see smoke in the distance it gives me a warning to turn off my HVAC. Is there anyway to resolve this? I am a company driver now and if I can just buy another air filter or something myself I would be willing to pay for it since having every bad smell blow in my face all day is getting old. If there is a bad smell or smoke outside it is coming right through my vents full blast every time. I am trying to do research on it so I am guessing perhaps my company I drive for uses the cheapest cab filter ever which is what the problem is?

 

Yes 100% sure if any air is coming through my vents whether it be the heater in the winter time or the cold air during spring/summer the second I see smoke it is blown right in my face to a point where I sometimes cough since it is thrown right in my face full blast through the vents. If it is outside it is coming through my vents. This isn't minor I can handle smells but when smoke is thrown right in my face and I can taste it then it is cause for concern. Also snowwy this happens while driving not parked. It comes through the vents of the dashboard. To the other poster yes I know about the door air I actually managed to stop most of that (wont go into detail) I am referring to the HVAC vents on the dash while the AC or heater is on. If you guys don't know what I am talking about then I can only assume my company probably doesn't even have a cab air filter and the air is just sucked from outside right into my cab. I need to unscrew it and check it tomorrow. I just learned about that after I created this topic from a Youtube video.

 

One thing for sure it is coming from my vents no question about it. I like for my vents to face toward me and I can feel the air and when a bad smell is present outside it is blown on me through the vents. If someone lit a fire outside and I go into my truck which is not running, wont smell a thing. Then I start it and the AC or heater starts blowing and all of that smoke will be in my cab immediately. The company I drive for is run by 21 year old college kids who do not know what they are doing so I wouldnt be surprised if they do not even have an air filter in these trucks to save on costs. They make other mistakes too such as the cutouts not lining up with the reefer tank on the side skirts and a lot of other mistakes that only an experienced driver would know.

 

So no for sure answers to this?