The FAA delegated safety to mfgs. (ODM), which in general doesn't work as well as expected.
The actual 737 Max design problems were caused by Boeing, then false documents were filed with the FAA, so you could argue that beyond the ODM system, Boeing deliberately misled the FAA, subverting the safety certification process.
The challenge with cockpit/cabin air quality is that fundamentally air flows from high pressure to low pressure in both a local as well as a global manner. So each airplane model and perhaps each example would need to be studied for air quality. Although airliners are air-tight pressure vessels, I don't think this is as simple as one might think.
I also have noticed strange smells or emissions in the cabin on some flights, so it appears to be a real issue. What people don't understand is that an airliner is a big machine beyond human scale, so even a minor problem on the scale of an airliner can have a big effect on a row of passengers.
Source: commercially-rated pilot, study aerodynamics.