We investigated submicron-sized aerosol filtration and the pressure drop of an electret filter called a “Flimmer filter.” The fibers of the filter are aligned parallel to the direction of the airflow, unlike conventional fibrous filters or conventional electret filters. Lab-scale tests were performed first in a laboratory duct system for submicron particle removal efficiency and pressure drop of the filter. Then, Field tests were conducted in an apartment home using two portable aerosol spectrometers and with a Flimmer filter installed at the terminal of a duct within a mechanical ventilation system. The removal efficiencies at the face velocity of 1.0 m/s for 0.4 μm and 0.6 μm were 52% and 65%, respectively. The removal efficiency for PM1.0 was about 51%. Through an adapted mass balance model, indoor particle concentrations both in number and mass were predicted. The predicted results for the temporal variations of 0.4 and 0.6 μm sized particle, and PM1.0 correlated well with the results obtained from the field tests. When the face velocity was 1.0 m/s, which is the nominal operating condition of the test filter, the pressure drop was 11.5 Pa, which is relatively lower than the pressure drops of other conventional fibrous filters or conventional electret filters having the same filtration efficiency.