Air particle counters

Malvern Autocounter 300A Air Particle Counter is designed for general cleanroom and environmental monitoring. It is a 0.3 pm to +5 pm, 1 cfm... 

One of SACHEM s products is tetramethylammonium hydroxide (TMAH), which is sold to semiconductor industries. Suspended particles in TMAH solutions could cause severe mechanical damage to the electronic devices manufactured by their customers. The determination of the particle content in such solutions is therefore critical. It is performed with a laser-equipped particle counter, which provides 70% detection efficiency. The counting must take place in a clean room because tiny airborne particles can land in the solutions and give them a false high reading. A class 1000 environment is required in this case, which means that the count of particles in the air that are greater than or equal to 0.5 jrm in diameter must be less than 1000 per cubic foot. Typically, a customer s specification for TMAH solutions is less than 100 particles per milliliter for particles greater than or equal to 0.5 fim in diameter. 

Direction of air flow Counter-current air flow gives higher particle density than co-current flow... 

The basic instrumentation in the present work is a Royco Model 225/518 High Concentration Particle Counter. The location of the air inlet and light sensing unit of the instrument in the card room has been described previously (2). The inlet was fitted with a vertical elutriator preseparator designed to prevent particles >15 vin aerodynamic diameter from entering the light sensor. Thus the collection efficiency of this instrumentation as a function of particle size should be similar to that of the Vertical Elutriator Cotton Dust Sampler. 

The number distribution of particles having diameters from 0.03-10 urn was measured twice daily on most weekdays with a Thermo Systems electrical aerosol analyzer (EAA) ( ) and a Royco Model 202 Optical Particle Counter (OPC). These measurements were performed at a site three miles southeast of the air... 

There are several different approaches that are commonly used to determine particle size distributions in air. One of them, impaction, has been discussed earlier. Multistage impactors with different cut points are used extensively to obtain both mass and chemical composition data as a function of size for particles with diameters > 0.2 /xm. Others, including methods based on optical properties, electrical or aerodynamic mobility, and diffusion speeds, are described briefly in the following section. The condensation particle counter (CPC) is used as a detector in combination with some of these size-sorting methods. 

The particulate matter in air should be measured with a particle counter Sampling procedure... 

If smoke is introduced with air pressure, adjust it to provide a smoke outlet velocity equal to the room air velocity at that point. Operate the particle counter with the sample tube at the normal work level and at a point remote from the smoke source. Verify that the counter indicates particle concentrations less than 200 particles of 0.5 ftm or greater. 

Particulate quantitative air sampling will be performed using device CI-500 innovation laser particle counter (serial no. mentioned on the monitoring format) according to SOP (provide number)... 

Only through discrete particle counting can air cleanliness be verified, and the cleanliness class of the sampled environment established. " Periodic in-process monitoring of workstations, buffer rooms, anterooms, production areas, and any other area about which a definitive air cleanliness statement is made or reasonably assumed, should be carried out in accordance with SOPs or industry standards. A discrete particle counter (DPC) with an adequate sampling rate, calibration features, and dynamic range should be used for sample acquisition, based on the specified air cleanliness level. ... 

Particles, moisture, soot, heat, air, glycol, fuel, detergents, and process fluids are all contaminants commonly found in industrial lubricants and hydraulic fluids. However, particle contamination is widely recognized as the most destructive contaminant to the oil and machine. This is the reason why the particle counter is the most widely used instrument in oil analysis today. The central strategy to its success in reducing maintenance costs and increasing machine reliability is proactive maintenance. 

The limit of detection of an optical particle counter depends on instrument noise, Rayleigh scattering by the air molecules, and stray light resulting from imperfect optics. For commercial counters with an incandescent light source, the limit of resolution is about 0.3 /tm. Instruments with laser light sources can go down to about 70 nm. 

For the optical particle counter of Fig. 6.5, the sensing volume is 1.5 x 1.5 x mm. Determine the total energy scattered by the air molecules in the volume. Compare this with the scattering by single particles with diameters ranging from 0.05 to 5 / m and a refractive index of 1.5. Assume k = 0.5 m and express your answers in terms of the incident intensity. The temperature is 20 0,... 

Certain precautions such as the siting of the production facilities in zones with little pollution, and providing dust-free, filtered air in production areas, limit pollution. Nonetheless, only the preparation of homeopathic dilutions in a cubicle with a controlled environment where the air is purified succeeds in eliminating pollution. These cubicles with laminar air flow which are employed for the preparation of homeopathic dilutions must comply with the limits of the class 4 000 for particulate contamination less than 25 particles of diameter equal to or greater than 5 p per m3 and less than 4 000 particles of diameter equal to or greater than 0.5 p per m3. The efficacy of air filtration inside the cubicle must be monitored regularly by means of a particle counter. 

In a study of the impact of printers as emission sources of VOCs, ozone and particulate matter on indoor air quality, ultrahne particles have been measured using Scanning Mobihty Particle Spectrometer-Condensation Particle Counter (SMPS-CPC) (Kagia et al. 2007). SMPS distributes from 20 to 500 nm diameter particles and CPC counts ultrahne particles. 

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