manufacturing is required. Examples of these industries include: semiconductor manufacturing; electronic component manufacture and assembly; photonic and optics manufacture and assembly; aerospace; pharmaceutical and biotech production; medical device manufacturing; cosmetics production; and food and beverage production. They are also used in industrial applications such as oil and gas, hydraulic fluids and automotive assembly and painting. A primary use of aerosol particle counters is in the determination of contamination levels within a cleanroom or clean containment device. Cleanrooms and clean containment devices maintain low levels of particulate-free air through the use of filters and are classified according to the number of particles permitted; the primary standard for cleanroom or clean air devices is ISO 14644-1, other local standards may also exist such as FED-STD-209E. Electronics Electronics manufacturing, and electronics assembly requires stringent environmental controls, especially where processes are performed within reactive conditions. Yields are reduced when components are contaminated with particles, and trace elements. Particle counters demonstrate that these controls are effective, and the production environments are optimized for the quality required. Depending on the application and size of the particles of interest, different instrumentation is required. General environments Air particle monitoring is required for ensuring the manufacturing environment is free from contamination level that will cause defects. It is performed either for the entire cleanroom areas (ballrooms, bays and chases), or specific local controlled environments (tools and minienvironments). Where large areas are to be monitored a manifold can be used, a manifold is a device used to connect many sample locations via sample tubing lengths, to a central stepper device and a central particle counter, it will sequentially move between tube locations taking a read from each location. Smaller spaces can be monitored using small point of use particle sensors, these are dedicated to sampling at a single location and rely on either a central vacuum supply or an internal sample pump. The contaminant particle size and frequency of measurement are factors in determining which method is most suitable. Liquid systems There are two primary liquid applications in the electronics manufacturing processes, fabrication process chemicals and ultra clean water for cleaning and rinsing. Process chemicals are used in semiconductor and other critical product processing steps (chemical etch, mask removal and chemical mechanical polishing). Particle monitoring in process chemicals, from manufacture through to the point-of-use, is extremely important for these clean processes to be controlled to ensure yield and throughput quality.