Patent ID: 7145320

Claim:
A particle counting method, comprising the steps of: taking in as aerosol flow a process gas in a process apparatus disposed in a clean zone for conducting a physical or chemical reaction in a vapor phase; charging particles existing in the aerosol flow; applying voltage to a conductive cylinder disposed in the aerosol flow having been subjected to the charging process to thereby electrostatically attract and remove floating ions included in the aerosol; then introducing clean air from the clean zone and generating a non-charged sheath gas flow shaped like a laminar flow in the periphery of the conductive cylinder disposed in the aerosol flow and mixing the sheath gas flow with the aerosol flow, and then applying an electrostatic field to the conductive cylinder to thereby classify the particles existing in the aerosol flow by getting the respective particles into traces deflected depending on their particle sizes; and detecting particles having specific traces deflected and measuring the spatial number density of particles to thereby calculate the particle size distribution of the particles floating in the process apparatus.