How Specialty Gases Differ from Industrial Gases Written by Bob Davis
When it comes to compressed gases, there is often confusion over difference between industrial gases (sometimes referred to as commodity or bulk gases) and specialty gases (sometimes referred to as cylinder gases, although industrial gases can also be supplied in cylinders). The Compressed Gas Association (CGA), who sets standards to which suppliers of all types of compressed gases conform, defines its mission as being “dedicated to development and promotion of safety standards and safe practices in industrial gas industry.” In a broad sense, in that most compressed gases are used for some sort of industrial application, all could be considered to be industrial gases. So to define true difference between industrial gases and specialty gases, one must look beyond application to other factors such as complexity, level of purity and certainty of composition. According to CGA compressed gases are often grouped into five loosely defined families: atmospheric; fuel; refrigerant; poisonous; and those having no obvious ties to any of other families. Assignment to these families is somewhat arbitrary and typically based on origin, use or chemical structure of a gas. Specialty gases can belong to any of these five families. Essentially, they are industrial gases taken to a higher level. The dictionary describes one of definitions of word specialty as: an unusual, distinctive, or superior mark or quality. Specialty gases then, can be defined as high-quality gases for specific applications that are prepared using laboratory analysis and other preparation methods in order to quantify, minimize or eliminate unknown or undesirable characteristics within gas. Regarding specialty gas mixtures, precise blending is also necessary to achieve very specific concentration values for components contained within mixture. Specialty pure gases Pure gases are considered to be specialty gases when they are used as support gases for laboratory instruments such as chromatographs, mass spectrometers and other various types of analyzers and detectors. Manufacturers of these types of highly sensitive instruments normally specify purity level of pure gases to be used with their instruments. For example, high-purity, moisture-free helium is often used as a carrier gas in these instruments. When unwanted impurities are present, performance of a laboratory instrument may be compromised, or instrument itself may be damaged. A good rule of thumb is, when purity (sometimes as high as 99.9999%) and/or quantification of trace impurities is an issue, a pure gas is considered to be a specialty pure. Specialty pure gases are used in manufacturing of semiconductors and other closely controlled applications as well. They may also be used to assess and monitor integrity of a bulk pure gas. Carbon dioxide is a good example. Beverage-quality CO2, as used in manufacture of soft drinks, can be classified as being more of a bulk-type gas because it is used in large quantities. However, because purity is a health concern, a specialty pure CO2, in which all trace impurities have been carefully quantified, is needed to calibrate instruments used to monitor purity of bulk CO2. Specialty gas mixtures Many specialty gases are actually gas mixtures that contain individual components. They are frequently used with various types of analyzers for process control and regulatory compliance. Some specialty mixtures are somewhat “standard” and may contain only three or four components, such as nitric oxide and sulfur dioxide mixtures that are used by utility companies to calibrate Continuous Emissions Monitors (CEMs). Others may be quite complex, containing as many as 30 or more components. Usually, a specialty gas mixture is prepared using a Standard Reference Material (SRM) in order to validate accurate measurement of mixture’s components. This provides what is known as traceability to a known measurement standard from a recognized metrology institution such as National Institute of Standards and Technology (NIST). Specialty mixtures typically have components measured in percentages, parts-per-million and parts-per-billion.
| | New Evidence Shows The Lasting Effects of Pesticide ExposureWritten by Dave Saunders
A new study suggests that moderate exposure to pesticides could yield long-term negative results to people exposed to them. These findings should serve as warning to those who indiscriminately spray pesticides around house, exposing their children, pets and other loved ones. This new research shows that farmers who used agricultural insecticides experienced increased neurological symptoms, even when they were no longer using products. Data from 18,782 North Carolina and Iowa farmers linked use of insecticides, including organophosphates and organochlorines, to reports of reoccurring headaches, fatigue, insomnia, dizziness, nausea, hand tremors, numbness and other neurological symptoms. Some of insecticides addressed by study are still on market, but some, including DDT, have been banned or restricted. These findings will be available online in April, and published in June issue of Environmental Health Perspectives. The research is part of ongoing Agricultural Health Study funded by National Institute of Environmental Health Sciences and National Cancer Institute, two of National Institutes of Health, and Environmental Protection Agency. "This research is really important because it evaluated health effects of agricultural chemicals as they were commonly used by farmers. It's different from previous studies that focused on pesticide poisoning or high dose exposures, for example when large amounts of a chemical were accidentally spilled on skin," said Freya Kamel, Ph.D., a researcher for National Institute of Environmental Health Sciences (NIEHS). Researchers found that nearly 3,000 participants had a high lifetime exposure to insecticides--that is, they used insecticides more than 500 days in their lifetime. Nearly 800 of these farmers reported more than 10 neurological symptoms compared to those using insecticides fewer than 50 days. The researchers found no significant association between neurological symptoms and other chemicals, including herbicides or fungicides, and only a weak association between fumigant exposure and neurological symptoms. Researchers found that nearly 3,000 participants had a high lifetime exposure to insecticides--that is, they used insecticides more than 500 days in their lifetime. Nearly 800 of these farmers reported more than 10 neurological symptoms compared to those using insecticides fewer than 50 days. The researchers found no significant association between neurological symptoms and other chemicals, including herbicides or fungicides, and only a weak association between fumigant exposure and neurological symptoms.
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