A vehicle passenger compartment air filter device comprising a filtration medium comprising (i) a first filter layer comprising a electrostatically charged split fiber nonwoven web layer and optionally a scrim affixed to said split fiber layer; (ii) a nonwoven web of electret charged thermoplastic microfibers as a second filter layer, said microfibers having an effective fiber diameter (EFD) of greater than 10 µm and comprising a thermoplastic resin having a resistivity greater than 10 14 ohm . cm and an additive selected from fluorochemical compounds or oligomers, organic triazine compounds or oligomers, hindered amine compounds, aromatic amine compounds, nitrogen containing hindered phenols, metal containing hindered phenols and mixtures thereof; said web having a basis weight less than 60 g/m 2 ; and (iii) a support layer made of a web material having an air permeability of 3750 l/(m 2 xs) or more at 200 Pa; said first filter layer being upstream from said second filter layer and said support layer being downstream from said second filter layer, wherein the first and second filter layers and the support layer are co-pleated and substantially non-bonded to one another except optionally at one or more of the outer edges of the filtration medium.