Characteristics of DC or Pulsed-Type High-Electric Field Plasma and its Application to Air Cleaning System

DC or pulsed-type high-electric field plasma (HEFP) is investigated. Here, HEFP means that no discharges take place in atmospheric environment, and strong electric field less than about $3 \times 10^{6}$ v/m is produced to accelerate free electrons to high energy for decomposition of chemicals, water vapor, or killing bacteria. In order to produce HEFP, two types of high-voltage exciter such as: 1) short rise time pulsed-type high voltages or 2) dc high voltages are used. The phenomena observed are slightly different between two types of high voltages in addition to the consumed electric power. The main purposes of the present studies are to show the typical characteristics of HEFP, including trapping of microdust particles with diameter $0.3~\mu \text{m}$ or larger, in addition to decomposition of chemicals and sterilization. The dust particles are perfectly trapped by adding HEFP with dc voltages, while in the case of pulsed HEFP, 100% trapping of dust particles was not observed at present. The decomposition of chemicals and bacteria sterilization is confirmed in both HEFP structures. These phenomena are applied to make new type of air cleaner working in the rooms such as private small rooms or hospitals with many patients staying at the same time or in the moving vehicles.