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Air Liquide

The world leader in gases, technologies and services for Industry and Health, Air Liquide is present in 80 countries with approximately 68,000 employees and serves more than 3 million customers and patients*. Oxygen, nitrogen and hydrogen are essential small molecules for life, matter and energy.​ They embody Air Liquide’s scientific territory and have been at the core of the company’s activities since its creation in 1902.

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An industrial process, an equipment or a medical device using a gas or a gas mixture

Autoignition temperature (IEC 60079-10-1)

Lowest temperature (of a surface) at which under specified test conditions an ignition of a flammable gas or vapour in mixture with air or air-inert gas occurs.

Autoignition temperature (ASTM E659)

The minimum temperature at which autoignition occurs under the specific conditions of test. It is the lowest temperature at which the substance will produce hot-flame ignition in air at atmospheric pressure without the aid of an external energy source such as spark or flame.


The action of using chemicals to whiten and/or disinfect matter such as clothing, wood pulp and material surfaces.

Carrier Gas

The gas used to carry vapor through the column of a gas-liquid chromatograph, known as the mobile phase

CAS number

The Chemicals Abstracts Service (CAS) assigns this number to each chemical substance, whether it is a specific molecule, a mixture of isomers, or a product created from a defined industrial process. Considering the complexity of the chemical nomenclature and the possibility to designate a chemical substance by several names, the CAS number makes it possible to identify each compound without any ambiguity.

Critical Point

This point is defined by a temperature and a pressure at which, for a pure substance, the properties of the two phases (liquid and vapor) are identical. On a phase equilibrium diagram, it is the highest temperature and pressure of the Liquid-Vapor saturation curve.


The use of temperatures below -150°C  to condense organic compounds contained in air or in a gas mixture with the objective to clean the gas and/or to recycle the organic compounds.


The metallurgy process of reducing the carbon content of a metal, usually steel.


In this process, a chemical is used to remove layers from the surface of a metal surface. A masking material is used to protect the surface not to be removed. Originally used to create artistic printing, it is today a key process for the fabrication of semiconductors.


Flashpoint (IEC 60079-10-1)

Lowest liquid temperature at which, under certain standardized conditions, a liquid gives off vapours in a quantity such as to be capable of forming an ignitable vapour/air mixture.


IOELVs are health-based indicative occupational exposure limit values that are derived by the Scientific Committee on Occupational Exposure Limits (SCOEL) from the most recent scientific data available and adopted by the Commission taking into account the availability of measurement techniques. They are threshold levels of exposure below which, in general, no detrimental effects are expected for any given chemical agent after short-term or daily exposure over a working lifetime. 

In accordance with SCOEL recommendations, IOELVs are established in relation to a reference period of 8 hours time-weighted average (indicative long-term exposure limit values, ILV-8h) and, for certain chemical agents, to shorter reference periods, in general 15 minutes time-weighted average (indicative short-term exposure limit values, ILV-15 min), to take account of the effects arising from short-term exposure.

Lower flammable limit (LFL) (IEC 60079-10-1)

The concentration of flammable gas, vapour or mist in air below which an explosive gas atmosphere will not be formed.


A process used to preserve a perishable product or make material more convenient for transport by removing the water in contain.  Also called freeze-drying, it is taking place in two steps : first the material is frozen, and then the surrounding pressure is lowered so as to release the solid water as gas (sublimation).


A chemical reaction between two species that entails the redistribution of chemical bonds. In olefin metathesis, fragments of alkenes are redistributed between two species by the scission and formation of carbon-carbon double bonds.


In the United States, occupational exposure limit values (OELs) have been established by federal agencies, professional organizations, state or regional authorities, and others.

OSHA Permissible Exposure Limits (PEL) (under the United States Department of Labor) [29 CFR 1910.1000 (2003)] are legally binding OELs, applicable to workstations covered by the Occupational Safety and Health Act (OSHA). PELs are 8-hour time weighted averages (TWAs) unless otherwise indicated (the ceiling value should not be exceeded at any time).



The occupational exposure limit value (OELV) to a chemical (defined in Article R. 4412-4 of the Labor Code) represents the concentration in the air that a person can breathe for a determined time. At this level, no organic or functional impairment of an irreversible or prolonged nature is reasonably foreseeable. The value is expressed in volume (ppm or part per million), in weight (mg / m3) or in fibers per unit of volume (f / m3).

OELV 8h (FR): The 8h-occupational exposure limit values (OELV 8h) are measured over a working period of 8 hours. They are intended to protect employees from the delayed effects of pollutants. 

OELV ST (FR): The short-term occupational exposure limit values (OELV 15 min)are values measured over a reference period of 15 minutes. They are intended to avoid toxic effects due to peak exposure (short-term exposure).



In oxy-fuel cutting, a torch is used to heat metal to its autoignition temperature. A stream of oxygen is trained on the metal along the cutting line. The metal, once burnt, flows out as a metal oxide slag.

Reflow Soldering

Reflow soldering is a method of assembling metal components on a circuit board surfaces


When taken above its critical temperature and pressure, a gas is becoming a supercritical fluid, combining liquid and gas properties.

Triple Point

In a pressure-temperature phase diagram, the triple point is defined by the pressure and temperature at which a pure substance (one sort of molecule) can be together liquid, gas and solid. Its three physical states coexist. The three phrase equilibrium curves (Liquid/Vapor, Solid/Liquid and Solid/Vapor) meet at the triple point.

UN Code

A Substance ID Code for goods whose transport is regulated. It is expressed as a four digit ID number, as for example : the UN code for argon in a gaseous state is UN1006 and in a refrigerated liquid state is UN1951.

Upper flammable limit (UFL) (IEC 60079-10-1)

The concentration of flammable gas, vapour or mist in air above which an explosive gas atmosphere will not be formed


A wafer is a thin (less than 1 mm) circular (typically from 25 to 300 mm) slide of semiconductor material such as crystalline silicon. Wafer are used for the fabrication of integrated circuits, semiconductor devices (transistors, ...) and photovoltaic cells