Specialty gases: definition and classification

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People quite often get confused between specialty gases and commodity gases. The confusion, however, stems from the fact that there is no clear definition accepted or released by the concerned authorities. Since the role of specialty gases in a number of industries, including materials processing, environmental, semiconductors, foods, chemicals, medical and biotechnology, defining the special class of gases is important. Therefore, here we try to define and classify it, which aligns well with its critical applications in various industries.

Traditionally, gases are defined and classified based on the application; for instance, fuel, atmospheric, poisonous, and refrigerant. Specialty gas does not fit entirely to any of the terminologies, as it can belong to any of the above-mentioned gases. Therefore, defining and stating its difference from other industrial gases requires focusing on factors like on the degree of purity, homogeneity in composition, and complexity, rather than on application.

One way to define specialty is: the industrial gases that take purity to a different level. In other terms, a class of gas purified to reach an absolute level of homogeneity in terms of composition for specific industrial applications. Preparation of the gases involves quantifiable methods and laboratory analysis with the objective to eliminate or to minimize — in those cases when complete purity cannot be achieved — unwanted properties in the gas. Additionally, based on the requirement, certain gas mixtures also come under specialty gas, where different gases are blended precisely for achieving specific concentration. Evidently, a single definition cannot describe entirely, and therefore, for practical purpose, they are classified as pure and mixtures.

Pure specialty gases

Such gases majorly have application in a calibration of various laboratory techniques, such s chromatography and mass spectrometry. When they are used in the laboratory setting, they often are termed as calibration gases — the most common is moisture-free helium. As laboratory instruments are highly sensitive, the specialty gas suppliers and manufacturers employ highly sensitive devices and apparatus to achieve the high level of purity, which deem gases acceptable to experiment purposes. Another common application of pure specialty gases is in the semiconductor industries, where they are crucial in the manufacturing process. Similarly, in the beverage industry, pure gases are used to monitor or asses the bulk pure gases, such as CO2.

Mixture specialty gases

A large proportion specialty gases are mixtures. As the gases have application in hundreds of industries, there is no definite number for specialty mixtures available on the market. Unlike purity gases, the mixtures have applications mainly in the industry, mainly for analyzers, which extensively are employed in the process control as well as in regulatory compliance. Based on the need of the industries, the mixtures are manufactured with a different number of components, going up to 30 components; although, the standard mixtures typically contain two to four components. The most extensively used mixture contains sulfur dioxide and nitric oxide, which is an important component in continuous emissions monitors. Commonly, preparation of the mixtures involves standard reference material for validation of the measurement of components proportion — components are measured either in parts-per-million or parts-per-billion.