Increased awareness of health effects caused by airborne contaminants that include natural and industrial aerosols, bioaerosols and gases, has led to increased usage of various kinds of filters. This trend is reflected in the automotive industry, where cabin air filters are increasingly offered as a means to reduce the likelihood of inhaling these contaminants while driving. Pleated filters, typically employing charge enhanced, thermoplastic base non woven media, have most commonly been applied in order to achieve the requisite level of particle capture, at minimum expense of additional burden to the vehicle HVAC system.The reliability of these filters, however, has been under scrutiny. This is particularly true for those derived from depth electrostatic media. In this study we have evaluated a newly developed depth media, as well as a split fiber electret media, under various simulated environmental and loading conditions. Loading evaluations were made on a filter test system with a vertically configured test duct section measuring 61 cm square. Filters were evaluated following loading with SAE fine dust, and following cyclic environmental exposure over the range -40°C to 90°C and relative humidity ranging from 0 - 98%. The test aerosol employed for efficiency determinations was SAE class Ultrafine.The introduction of fine meltblown fibers within a depth media appears to significantly moderate the decay characteristic on aging often associated with depth solutions. The particle penetration for an automotive cabin air filter was compared between laboratory filter test as observed with optical counter, and in vehicle testing with sampling by means of aerodynamic particle sizer.