From what I understand there is a standard filter and a charcoal activated filter. They are both located under the large plastic panel under the hood. Im not sure but I read somewhere there is a third that might go in under the dash somewhere. I have yet to change mine and would be interested myself to know from someone who has done the changing.

Additionally how often is the "realistic" interval to change these filters. The charcoal one is rather pricey and Im rather sure the interval in the manual is profit motivated rather than need motivated for the frequency of the changes.