To make a fuel cell work, you need an external oxygen supply for the chemical reaction. A cleaner oxygen supply with fewer particles make the fuel cell work lon

To make a fuel cell work, you need an external oxygen supply for the chemical reaction. A cleaner oxygen supply with fewer particles make the fuel cell work longer, therefore Hyundai added an air filter which filters out fine particles before passing it on to the fuel cell. (I'm not an expert, but this is how I understood the process.)