As far as i know it has no such filter, it's an older car originally designed in 1988 and mines a 1995 model when the line ended but basically not much changed. It could be the ventilation is more restrictive internally than my previous car... that was a 1985 opel kadett and after it was parked under a tree for quite a while bits of leaf would blow out of the vents
None of that on this car fortunately, so perhaps there is some sort of filter internally. The fan looks like some kind of hamster wheel so that should make for some restriction too when it's not turning... Still when you design a more restrictive ventilation system wouldn't it be logic to try and tap into the ram effect even more to compensate?