What Is Isokinetic Sampling?

Isokinetic sampling collects particles in a moving stream which moves at the same velocity in the sampling nozzle as elsewhere in the stream. This can increase the accuracy and reliability of results. It is used for activities like monitoring pollution in factory stacks, taking general air samples in an area of interest, and checking equipment for dust and other concerns. Numerous products are available for this purpose from suppliers of scientific and testing equipment. A technician may be needed to collect samples and install equipment.

The term “isokinetic” comes from root words meaning “same” and “movement.” In an isokinetic sampling procedure, the testing nozzle is set up to allow the sample stream to enter without changing speed. This reduces the risk of concentrating larger or smaller particles. If the stream moves too slowly into the collector, it increases the number of large particles. Too fast, and large particles are lost. In either case, the sample collected wouldn’t be an accurate reflection of what is in the overall stream.

It can be costly and painstaking to perform isokinetic sampling. For certain applications, this technique may be recommended or required by law to get the most reliable and useful results. In other cases, technicians may feel it is appropriate, and worth the additional effort to get the best possible sample. Some applications do not require the use of isokinetic sampling, and can be handled with other techniques for testing and assessing the contents of a stream.

Systems like factory stacks may have in-line sampling devices left in place at all times. They regularly take readings and record data. If a problem arises, some can send signals to alert technicians to a problem, like an unacceptably high number of particles in the air. These safety systems are designed to reduce risks to the public and the environment by catching problems as early as possible. Periodic cleaning, maintenance, and calibration are necessary to keep them working properly.

In other cases, an isokinetic sampling station can be set up for specific testing purposes. A technician can assess the situation to determine which equipment to use and how to position it. Sample collection may be repeated to confirm results before the technician writes up a formal report on what was found in the testing. Chemists, air quality specialists, and other scientists may have the qualifications needed to collect and discuss readings, and can perform them for government agencies, consulting firms, and private companies.