Are you asking about engine air filtration or cabin air filtration?
Engine air filtration, I would assume there are not any, as such would cause a lot of air flow restriction. I would also recommend against making your own as the most critical part of a new air filter is the outer seal, as in the absence of a good seal, a significant amount of air will flow around the filter rather than through it (following the path of least resistance), allowing the resulting unfiltered particles free reign in your intake system.
As for cabin filtration, the question becomes, "Why?!?". Any benefits gained through such high levels of filtration will be lost as soon as you open the car door to exit or roll down your window at a fast food restaurant. And it would become so quickly clogged at the microscopic level that you would have to replace it very often.