Term Description
ACGIH American Conference of Government Industrial Hygienists, an organization dedicated to promoting occupational and environmental health, including setting standards regarding acceptable levels of exposure to potentially dangerous materials.
AIHA The American Industrial Hygiene Association, a nonprofit organization dedicated to keeping occupational and environmental health and safety professionals who work in industry up-to-date regarding their field.
Alarm Only Instrument A device designed to serve only as an alarm in case of danger; does not provide diagnostic information.
Alarm Set Point The point at which an alarm is calibrated to sound when the concentration of a specified gas reaches an unacceptable level.
Ambient Air Term for air normally found in the environment, roughly 21% oxygen and 79% nitrogen.
Anaerobic Oxygenless gases that aid in the growth of various biological cultures.
Analyzer Used to measure elements in a mixture, both qualitatively and quantitatively.
Approved Signifies the satisfaction of criteria. Deemed safe or appropriate. Also “listed” or “certified.”
Area Monitor A very specific term, requiring for gas sensors that the instrument measure precisely the saturation of a component in a pre-determined area.
Asphyxiant Gas Any gas that, when released, will replace oxygen in the environment, eventually causing death for oxygen dependent life forms.
ASSE The largest organization for professional safety, the American Society of Safety Engineers was founded in 1911, making it the oldest as well. Spanning across sectors from government to insurance, from education to industry, the ASSE also works with the Occupational Safety and Health Administration (OSHA) to solve and prevent issues. One way ASSE prevents safety issues is through awareness, and it is involved with North American Occupational Safety and Health Week (NAOSH).
ASTM American Society of Testing Materials. They are responsible for setting standards for industrial practices and transactions. Contrary to their name, they influence committees on a global scale.
Boyle's Law Indicates the inverse relationship between volume and pressure for an ideal gas at a constant temperature. This graphic from NASA illustrates this relationship.
Bump Gas This gas is normally kept in a round container and is used to like a spray paint to cover a sensor housing. Because it contains a very high concentration of gas, much higher than is needed for an accurate calibration to take place, it is never used for the calibration process.
Bump Test Procedure A qualitative function check in which a challenge gas is passed over the sensor(s) at a concentration and exposure time sufficient to activate all alarm settings.
Butane, (C4H10) With a molecular formula of C4H10, this is a very flammable gas that has no color or scent and turns to liquid very easily. Sometimes it is called n-butane and can refer to n-butane plus only one isomer called isobutane. Its CAS Number is 106-97-8.
Calibration Procedure (Full Calibration) Adjusts the instrument's reading to coincide with a known concentration (i.e., certified standard) of test gas.
Calibration Gas Standard If a gas is labeled with this designation, it shows that the mixture has been correctly compared to a known reference standard. This mixture can then be used on analytical instruments as a comparative standard in determinations.
Capillary Cell, (O2 Sensor) A system that measures the amount and type of gases by using electrical and chemical sensory methods. When the sensor is only trying to detect certain types of gases, this usually can happen easily inside of the components of the actual sensor. If the amount of gas is being measured, a technique is often used where a porous barrier is put over the sensor and gas is let through at a predefined rate. This creates a controlled gas exposure. The downside to this is that it is easy for the barrier to become clogged with dirt, thus throwing off the results of the test. A capillary gas sensor can totally eliminate the use of this porous barrier, replacing it with a solid one with a single opening in the center. Just like the porous barrier, the gas can pass through at a predefined rate. These sensors are also made for different altitudes and barometric pressures, unlike the Galvanic Electrochemical sensors. This helps create more consistency.
Carbon Dioxide, (CO2) CO2 is one made up of two oxygen atoms attached to one carbon atom. At normal pressure and temperature, this element is a gas, its normal form in Earth’s atmosphere. This gas weighs more than air, has a distinct displeasing odor, and has no color. Plants use this element to produce oxygen which is put into the air. It is also produced from the breath of animals and humans and from fermenting liquid. When coal or hydrocarbons combust, it also can result in the creation of this element. This element has a freezing point of -78.5° C (-109.3 F). At that point it turns into carbon dioxide snow.
Carbon Monoxide, (CO) The element with a molecular formula of CO contains only one carbon atom that is attached to one oxygen atom. This highly toxic, flammable gas has no color, odor, or taste. This gas is created when there is incomplete combustion that comes from too little oxygen. It your heating system is not taken care of, it can result in this being produced which can lead to death or serious poisoning. It can be useful on a larger scale though as some companies use it to help produce certain intermediary organic chemicals. Some of these include acetic acids, formic acid, isocyanates, and certain polymers like polycarbonates and polyketones. They create these organic chemicals by reforming the hydrocarbons.
Catalyst The term referring to a material that causes a chemical reaction to occur or to happen faster.
Catalytic Bead Sensor This sensor is made up of two coils of thin platinum wire that are ingrained in a bead of alumina. A Wheatstone bridge circuit connects the two electrically. When this happens, it causes one of the pellistors to gain a special catalyst. This causes oxidation to take place. In the meantime, the other pellistor is treated to keep it from oxidating. A current goes through the coils, causing them to reach a temperature at which oxidation of a gas can occur at the catalysed bead. That temperature is between 500° and 550° Celsius. As the process continues by the combustible gas going through, it causes the temperature to continue to rise. This increases the resistance of the platinum coil in the catalysed bead, which causes an imbalance of the bridge.
Celsius This is a temperature scale with 0° as the freezing point and 100° as the boiling point.
Certificate of Analysis (COA) This printed certificate guarantees to a client that the gas has been inspected to the indicated levels of purity or impurity.
Certified Concentration On a Certificate of Analysis or Accuracy, this is the concentration that is listed for the particular component. It shows the customer what concentration is represented by the component and how he should use that concentration. It is ok for the concentration to be blended or analyzed.
Certificate of Conformance (COC) This printed certificate lets the client know that a certain gas meets the required standard.
Colormetric Gas Sampling Tube Glass tubes operated by a pump mechanism that allow the user to measure various types of gases found in the atmosphere. The tubes contain reagents that change hue when they come in contact with different gases.
Compressed Gas Gas that is under greater pressure than is found in the surrounding atmosphere. When released, compressed gases can function as propellants.
Confined Space A term used by the Occupational Safety and Health Administration (OSHA) that refers to an enclosed area not normally designed for human occupancy. It is large enough for one person to enter but has limited access and is therefore dangerous. Such spaces are prone to the concentration of gases detrimental to human health and are subject to regulations regarding their air quality and rescue plans.
Corrosive Term describing a substance’s capacity for chemically wearing away or eating away at another substance, rendering it ineffective.
CSA Canadian Standards Association, or CSA Group; organization that develops global safety standards and certifies products.
Cylinder Used to contain and transport gases in a compressed state. Must meet government safety standards in design and quality.
Department of Transportation (DOT) Established by Federal Regulation Code Title 49, the DOT oversees hazardous substance transportation.
Environmental Protection Agency (EPA) Federal government agency set up to protect the environment and human health. Established December 1970.
EPA Protocol Mixture Mixture of gases formulated according to standards set by the Environmental Protection Agency.
Exposure Limits Legal limit set by the Occupational Safety and Health Administration (OSHA) to which employees may be exposed to potentially harmful substances in the workplace. When dealing with gases, usually measured in ppm.
Fahrenheit Scale for measuring temperature that originated with Daniel Gabriel Fahrenheit in the 1700s. Defined by the temperature at which water freezes (32° F) and boils (212° F).
Flammability Limits The upper and lower limits at which a given gas can ignite while mixed with air.
Flammable Gas A gas is classified as flammable if a 13 percent combination with air is flammable, or if its flammability range is wider than 12 percent.
Flash Point Described as the minimum temperature at which a gas emits flammable fumes into the air, creating the danger of explosion.
Fuel Cell Sensor, (ElectroChemical) This very efficient, useful device is a battery that runs on external gas, not components stored inside the battery itself. Converting plenteous elements like hydrogen and oxygen into usable energy, they are ideal for use in space. Most fuel cell sensors last between three and four years before becoming unusable.
Galvanic Electrochemical Sensor Galvanic electrochemical sensors operate by monitoring the decay of a metal cell when exposed to certain hazardous gases, such as hydrogen cyanide and ammonia. Their life span depends on the metal’s exposure to gas (usually less than two years).
Gas In a gas, molecules are very loosely bound together. An ideal gas is one that adheres closely to laws of gas behavior.
Gas Detector A critical device that monitors the atmosphere for gases that are harmful to life. These include explosive and poisonous gases like methane and sulfide, as well as oxygen deficiencies. A detector sounds an alarm when conditions are dangerous.
Heat of Vaporization The amount of heat necessary to change one mole of a given substance from a liquid to a gas under normal atmospheric pressure.
Hexane, (C6H14) Hexane is used in many practical applications. In scientific contexts, it can extract contaminants from samples. In everyday life, it appears in fuel, adhesives, and cleaning products.
Hydrocarbon A compound that includes hydrogen and carbon atoms.
Hydrogen Cyanide, (HCN) Hydrogen Cyanide has the molecular formula (HCN) and CAS # 74-90-8. It is often known by its odor, which is similar to that of almonds. It has no color but is very lethal as well as unstable. It has a boiling point that is somewhat above room temperature. It is a somewhat acidic, and it can also be partially ionized in a solution. Cyanides are important for laying the foundation of many pharmaceutical products as well as compounds that have undergone polymerization.
Hydrogen Fluoride, (HF) Hydrogen Fluoride is an element that is used for the calibration of equipment used to monitor emissions in the environment, as well as equipment that analyzes particle impurities. Those who work with glass and cement especially pay attention to the release of hydrogen fluoride. The element is a part of a variety of superacids. It is particularly odorous, and it is actually not as heavy as air. The boiling point is lower than room temperature. The use of hydrogen fluoride is especially prevalent in industries that deal in gasoline, petroleum, and other similar materials.
Hydrogen Sulfide, (H2S) In swamps and sewers, the breakdown of organic material called sulfates caused by a lack of oxygen can cause the build-up of hydrogen sulfide when there is no oxygen present. This in turn is the partial cause of the sulfur-like odor that is often smelled in such areas as sewers and swampy areas when anaerobic digestion takes place. Hydrogen Sulfide is molecular formula (H2S) CAS # 7783-6-4 UN1053 and it is the gas that comes about as a result of this anaerobic digestion as well as in volcanos, wells, and natural gases.
Although many people think that the sulfur-like odor comes from the element sulfur in these areas, this is not the case. Sulfer does not actually have any odor. Hydrogen sulfide is used to calibrate equipment that is used to monitor emissions. It is also used in detectors that check for industrial polution. Machines that analyze for small amounts of impurities also use this element. Some mixtures used for calibration also use hydrogen sulfide as a balance gas. It is not a gas that can be seen, as it is colorless, but it is very lethal and will ignite.
Hydrogen, (H2) Hydrogen is a complex element that has no odor, color, metal, or taste, but it will easily ignite. This element with molecular formula H2 and CAS # 1333-74-0 UN1049 was discovered in 1766 by Henry Cavendish and was named by Lavoisier. It is a scarce element, as it is only found in small amounts in the Earth’s atmosphere. Although it is scarce in the atmosphere, it is prevalent in water and petroleum products. It is the H in H20; there is no element that is lighter than hydrogen. It has an atomic weight of 1.00794.
Hydrogen is a very reactionary element, so caution must be used with it. Its use in fuels cells combined with oxygen produces an electrical charge.
Inert Gas An inert gas is one that is not volatile when under conditions of both temperature and pressure that are normal.
Infra Red, (CO2) Sensor An Infra Red Sensor is a tool that can find gases that have more than one type of atom. This tool can be used to find carbon monoxide, dioxide, sulfur dioxide, as well as methane. Some other gases cannot be found through the use of an Infra Red Sensor. Some examples include oxygen, chlorine, and hydrogen.
These do not have more than one type of atom. If you are seeking to separate out a particular gas through the use of Infra Red Sensors, then the absorbtion frequency for the various ones would need to be measured. Simple detectors for this use pumps with a lamp and IR sensor. It is set to a certain frequency so that when a specific gas is present, the Infra Red Sensor will detect it. An optical filter will do the measurements. When creating Infra Red sensor based gas detectors, it is essential for there to be linearising circuitry so that as the amount of gas entering the sensor accumulates, the signal will not be reduced as would normally be the case.
Inorganic Compounds Inorganic compounds have a molecular make-up that does not include carbon.
ISEA The International Safety Equipment Association is an organization that works alongside companies that provide equipment made to protect the wearer. This equipment might be used in hospitals, schools, or construction sites. It will vary by use, but it is important in many industries today as well as to people going about everyday tasks at home.
Isobutylene,(C4H8) Isobutylene (C4H8) is used in combination with other chemicals to manufacture products. It is used in the manufacturing of gasoline, the production of butyl rubber, and other industrial uses. It is a very important element for industry. It is an alkane that has four carbon branches. It is also an isomer of butylene. In its normal state, isobutylene will ignite; it has no color.
Kelvin A temperature scale using the pressure of water, gas, and liquid in an equal state which is also called the triple point of water.
Level of Detection In order for there to be a level of detection when using chromatography, there must be enough in a sample to create levels above the baseline by two or three times.
Liquefied Compressed Gas A gas that turns to a partial liquid when under charged pressure at 70° Fahrenheit.
Liquified Petroleum Gas (LPG) At a normal pressure and temperature, the existence of hydrocarbon gas in the form of a liquid.
Lower Explosive Limit (LEL) Minimum concentration of gas, at standard temperature and pressure (STP), needed to be combustible.
Material Safety Data Sheet (MSDS) An informational sheet used to describe various products whether hazardous or not to help the user understand how to handle the products and what dangers may exist with their use.
Metal Oxide Semi-Conductor Sensor, (MOS), AKA, Solid State Sn02 is a common metal oxide that is found in TGS (MOS) gas sensors. Oxygen is absorbed on the negatively charged, crystal exterior when a crystallized metal oxide is brought to a specific air temperature. The oxygen that has been absorbed then receives donor electrons, ultimately resulting in a positive charge.
This acts as a possible obstacle to prohibit the flow of electrons. The sensor itself has an electrical current that moves through crystals of Sn02. Because of this, the sensor has electrical resistance. There is a reduction in the height of the grain boundary barrier when there is a deoxidizing gas present. Sensor resistance is lessened with this decreased height in the barrier.
Methane, (CH4) Geiger counters and X Ray Fluorescence detectors make use of methane when used in combination with argon. Methane, (CH4) CAS #74-82-8 UN1971; UN1972, can also be put into a mixture with hydrocarbons when looking for the PCI of coal or hydrocarbons. In this use, it is a reference point for measurements that are calorimetric. Other uses of methane include calibration, monitoring, and analyzing in various petrochemical and environmental industries.
Methanol, (CH3OH) The simplest form of alcohol, Methanol (CH3OH) CAS # 67-56-1, has a number of other names. Other names that methanol goes by include carbinol, wood alcohol, wood naphtha, methyl alcohol, and wood spirits. This alcohol is a light-weight liquid that is not only toxic, but also flammable and unstable. It is also colorless. The odor is similar to that of alcoholic beverages, but it is sweeter. Methanol has several uses when it is at room temperature. It can be used for fuel, antifreeze, or as a solvent. It can also be used for ethanol as an amalgamation. Methanol has been used in the production of biodiesel.
Methyl Ethyl Ketone, (see n-Butanone) Methyl Ethyl Ketone is a butterscotch/acetone-scented ketone that is used in many industries. It is also called Butanone or MEK. The molecular formula is CH3C(0).
Methyl Mercaptan, (Methanethiol, CH4S) Methyl Mercaptan (Methanethiol, CH4S) is a substance that is found in nature. It is present in foods such as cheese and nuts. It is found in parts of the body such as the brain and blood. Plant and animal tissues also contain CH4S. It has no color, but has a strong, unpleasant smell. Another name for the substance is methyl+B119 mercaptan.
Micron A measurement of length that equals 1 x 10-6 meters.
Mole The molecular weight of a substance (in mass) which is commonly called grammole.
Molecular Weight In a substance, a single molecule’s weight is measured by adding up all the weights of the atoms.
Nanometer (nm) A measurement of length that equals 1 x 10-9 meters.
NIST Stands for the National Industrial Standards Testing – a U.S. Government Metrology Agency – which oversees measurements and standards in a non-regulatory manner.
Normal Temperature and Pressure A standard system of reference for the gas industry: temperature is 70° F and pressure is denoted as 14.696 psia.
Occupational Safety and Health Administration (OSHA) A Department of Labor agency that sets the standards for safe and healthy work environments. It also enforces these statutes and regulations and provides education, training and assistance to companies and organizations.
Oxidizing Agent A substance which will react to cause combustion or helps to cause combustion of other materials.
Oxygen, (O2) Accounts for 20.9% of the volume of the atmosphere and accounts for more mass in the earth’s crust than any other element, making it the third most common element in the universe after hydrogen and helium. It has applications in environmental emission monitoring, industrial hygiene monitors, industrial safety monitors, trace impurity analyzers, and the petrochemical industry, where it is a component in calibration gas mixture.
Parts per Million (PPM) Similar expressions are parts ber billion (ppb) or parts per trillion (ppt). Used to measure small amounts of elements present in mixtures. May be used with different units of measure, including moles, volume, or weight.
Pellistor, Catalytic Bead Sensor These sensors are made up of two Alumina beads, each containing a platinum wire coil. The beads are connected on an electrical bridge circuit. One bead is treated with an oxidation catalyst, and the other bead is treated to prevent oxidation. By passing a current through the coils, the beads are heated to about 940° F, the temperature at which oxidation occurs in one bead. The increased resistance of the coil in the oxidized bead causes the bridge to be imbalanced. The Catalytic bead Pellistor sensor is more commonly known as a “Wheatstone Bridge Sensor.”
Pentane, (C5H12) An alkane distinguished by the molecular formula C5H12. Isopentane and neopentane are the branched isomers of this organic compound which is very much like butane and hexane. Pentane is used in fuels and as a laboratory solvent.
Permissible Exposure Limit (PEL) The OSHA maximum allowance for work place exposure to various substances.
Phosphine, (PH3) This highly toxic compound appears regularly in pest control procedures in the forms of fumigation and aluminium, calcium, and zinc phosphide pellets. Phosphine is also used for forming borophosphosilicate glasses by PECVD, for doping polycrystalline or amorphous silicon, and is an N-type dopant for silicon emitters, source-drains, and collector contacts in semiconductors.
Photo Ionization Detector (PID) A gas detector that can provide real time information. PIDs can recognize gas concentrations from sub parts per billion to 10,000 parts per million. This very popular and effective detector that can monitor for ammonia detection, hazardous materials, arson investigations, air quality, environmental contamination, and remediation and cleanroom facilities contributes to safe working conditions in military, industrial, and confined work spaces.
Poison Any substance that can cause severe damage or death to living organisms when ingested, injected, absorbed, or inhaled in small doses.
Primary Reference Material (PRM) A National Institute of Standards and Technology (NIST) approved calibration standard.
Primary Standard Primary Standards are put together to close tolerances by weight. The analysis is compared against what is referenced in order to make a confirmation of weights. The Certificate of Analysis reports the method that is used in the determination of concentrations and uncertainties.
Propane, (C3H8) Propane is a versatile gas used in many different ways. It can be found in products from barbecue grills to vehicle fuel. When it is found in vehicles, other chemicals are added such as propylene, butane, and butylene. In this state, it is a liquid. Because it is a dangerous gas, an odor is added to propane to make leaks noticeable. Propane is a petroleum derivative product that occurs when oil and natural gas are processed. It has the molecular formula C3H8 and CAS #74-98-6 UN1978. It is an alkane with three carbons and can be in liquid form if compressed, but most of the time it is a gas. It is used for calibrating various equipment that analyzes for emissions and other environmental issues. It can also be used with atomic absorption analyzers as fuel.
Propylene, {Propene} (C3H6) In the alkene class of those elemental compounds derived from petroleum and petroleum bi-products, Propene (C3H6), also called propylene, is the second most simple. It is a living compound that is not saturated and has an individual double bond. There are several uses for this ingredient, including uses with gasoline and polypropylene. It also is used in detergents in the form of trimers and tetramers. Propene is also used for calibration various environmental, pollution control, and petrochemical industries.
Span Gas A gas used for calibration so that the scale and analyzer can have the maximal reading set correctly.
Specific Gravity A standard substance ratioed against the mass of another is refered to as Specific Gravity.
Standard Reference Material (SRM) NIST is responsible for this reference standard certification.
Standard Temperature and Pressure (STP) The standard temperature of 0° Celsius and the pressure of 14.6960 psia is a reference that is seen internationally as this set norm, known as Standard Temperature and Pressure.
Sulfur Dioxide, (SO2) Sulfur Dioxide (SO2), a substance that comes from volcanoes as well as industrial processes, is used in a variety of ways, including fumigation, bleach, preservation, or even in the production of grain. One of the applications of preservation with sulfur dioxide is in winemaking, because it can protect from microbes and oxidation. The substance is also used in monitoring, analyzing, and calibrating for environmental and petrochemical industries.
Thermal Conductivity (TC Sensor) Thermal Conductivity Sensors are inexpensive and long-lasting. Some great traits include their ability to stay calibrated with little maintenance. Part of the reason for the lack of maintenance is because they are low on chemicals that could change from their original state. They also lacks optics that could become misaligned. These tools are used to measure for several different gases. They do not have to have air as a background gas. This is another positive with this particular sensor. The sensor works by comparing a reference gas to that of a sample, which in turn causes a heat reaction by either increasing or decreasing the temperature based on the amount of thermal conductivity.
Threshold Limit Value (TLV) Level of a potentially hazardous material to which employees can be exposed over the long term without known negative health effects. Set by the American Conference of Industrial Hygienists.
Threshold Limit Value/Short Term Exposure Limit, (TLV/STEL) Threshold Limit Value (TLV): Level of a potentially hazardous material to which employees can be exposed over the long term without known negative health effects. Short Term Exposure Limit (STEL): Acceptable level of exposure to potentially harmful substances over a short period of time, usually 15 minutes.
Threshold Limit Value/Time Weighted Average, (TLV/TWA) Threshold Limit Value (TLV): Level of a potentially hazardous material to which employees can be exposed over the long term without known negative health effects. Time Weighted Average (TWA): Allows for the averaging of an employee’s exposure to potentially hazardous materials over a specified time period. That is, an employee’s exposure to potentially hazardous materials may go beyond limits normally considered healthful as long as the average over a specified period (usually 8 hours) overall is lower than the TLV.
Threshold Limit Value-Ceiling (TLV-C) Upper limit of an employee’s exposure to a hazardous substance that may not legally be surpassed.
Toxic Poisonous; material that when contacted, inhaled, or ingested causes harm and, ultimately, death to the one coming into contact with it.
Ultra Zero Air Lab-grade purified air consisting of < 5 ppm CO2, < 0.1 ppm CO, < 0.1 ppm HC, and < 1 ppm NOx.
Zero Gas A gas purified to an impurity concentration below an analytical instrument’s minimum detection limits. Used when calibrating instruments and testing other components.