I personally don't really agree with regression in this area but more than one automotive engineer has told me that things have gotten to where the exhaust must be cleaner than the air taken in by the engine.
1. There is an air filter that immediately takes out large particles (dust, dirt, mites, etc)
2. Emissions systems use hot wires to detect airflow precisely
3. O2 sensors readily adjusting fuel on the fly to ensure a complete burn.
4. A catalytic process using space metals that further ensures a clean burn
Effectively, whether it's dusty, a cow has farted around you, or a chicken farm is producing ammonia; the modern ICE has the ability to detect this scenario and adjust faster that 8k times a second.
And it isn't anyway. Just stand next to a running engine in a badly ventilated area for a while and you'll know that engine doesn't make things better.
CO2 or H2O concentrations are enough to make things worse for an engine or a human, but are not necessarily dirty.
NOX and CHs however are not as "naturally" in the air and producing them definitely makes the air "dirtier"
With regard to parent's assertions: 1. The intake air cleaner is to keep particles out that will damage the engine (and eventually lead to lower performance and emissions control malfunction); 2. Whatever airflow meter, or not, on an engine is for combustion control, but its performance affects emissions output; 3. Exhaust o2 sensors, for 10-25 years depending on make and model, have already been telling the control system the results of combustion on each cylinder, for every combustion; 4. The catalysts are not magic. They are meant to react with specific products of combustion; There is nothing in an automobile, nor should there be, to detect and react with things like methane and ammonia. The only time you see a dust/smog detection is in luxury models that adjust the cabin ventilation in the presence of this for comfort of the occupants. There are no adjustments happening at a rate of 8 kHz: combustion in a cylinder is not even happening at this rate.
Then the combustion and catalytic process will break apart that ammonia and encourage its nitrogen to linger on its own as the hydrogens burn up or find some oxygens.
Thought not.
Are they working on hydrogen based engines?
ICEs are better off converted to LPG or DME. CNG takes too much space and also uses higher pressure containers, while it can be easily converted to DME and stored in containers pressurized at 0.5 MPa.