Direct Reading Instruments for the Determination of Aerosols and Particulates

Abstract

Solid and liquid particles suspended in a gas are referred to as aerosols. The suspending medium can be air, or some other gases, such as argon, nitrogen, helium, etc. Aerosols have found numerous scientific and technical applications. Beneficial applications include pharmaceutical aerosols for medical inhalation therapy or diagnosis, industrial aerosols for coating wave guides, refractories, gas sensors and semiconductors, as well as particles ofmodern materials for forming advanced ceramics, optical and optoelectronic devices, cosmetic products, paint pigments, and catalysts. Harmful effects of aerosols include atmospheric aerosols that contribute to urban air pollution and global radiation balance, dust particles ingested by engines causing premature failure of the equipment, and particles deposited on semiconductor wafers causing device failure and product yield loss. Aerosols and particles can be analyzed by collecting them on a filter or a sampling surface for subsequent microscopic, gravimetric, or chemical analyses. The collection by the samplers gives an integrated sample and a time averaged concentration over a period of hours or days. Direct reading instruments carry out the sampling and analysis within the instrument and the property of interest can be obtained in near real‐time. Direct reading instruments are available to cover particles in the size range of 0.002 to 100 µm. These instruments have fast time response and can follow rapid changes in both particle size and concentration. Good counting statistics can also be obtained because repeated measurements can be performed in a short time. However, these instruments usually rely on indirect sensing techniques and more calibration efforts are usually required.

Interlaboratory Study of the Exhaust Gas Particle Number Measurement Using the Condensation Particle Counter (CPC)

“…If the particle-size distribution is ignored, the total exhaust particle number on steady speeds and cycles can be measured by a condensation particle counter (CPC), − which can determine the total particle number but not the size distribution of exhaust particles. The detailed operation principle of CPC is reported in several studies. ,,,,, …”