Hydrogen is the most abundant chemical element, constituting roughly 75% of the universe's elemental mass. Stars in the main sequence are mainly composed of hydrogen in its plasma state. Naturally occuring elemental hydrogen is relatively rare on Earth.
Hydrogen forms compounds with most elements and is present in water and most organic compounds. It plays a particularly important role in acid-base chemistry with many reactions exchanging protons between soluble molecules.
Hydrogen gas is highly flammable and will burn in air at a very wide range of concentrations between 4% and 75% by volume. Large quantities of H2 are needed in the petroleum and chemical industries. The largest application of H2 is for the processing ("upgrading") of fossil fuels, and in the production of Ammonia.
Airmet offers a wide range of portable and fixed gas detectors for detection of Hydrogen. Please note the difference between the ranges available (%LEL or ppm). Use the product selector to find the suitable instrument for your application.
Hydrogen Characteristics
CAS No. 1333-74-0
Chemical formula H2
Vapour density 0.07 (air = 1)
Safe Work Australia ES TWA --- (simple asphyxiant)
STEL ---
Flammable limits LEL 4.0 % by volume
UEL 77.0 % by volume
Equipment group IIC
Temperature classification T1
Chemical/physical properties Hydrogen is a colourless, odourless and tasteless gas at room temperature. It ignites easily, having a wide flammable range and an auto ignition temperature of 560 °C. It burns in air with a blue flame with water as the only product of combustion.
Hazardous properties Hydrogen has no toxic effects if inhaled but will act as an asphyxiant if present at a high enough concentration to displace oxygen below 18 % by volume.
Its major hazard is the risk of explosion due to its high flammability, accentuated by its high mobility (low viscosity) and low vapour density.
Occurrence/Uses Although Hydrogen is the most abundant element in the universe it only occurs naturally in the atmosphere at trace amounts (~ 1 ppm).
Its major uses are in the chemical industry (e.g. for the production of ammonia) and, due to its high thermal conductivity and low viscosity, as a coolant in power station generators.
Detectors available Catalytic bead (0 – 100 % LEL)
Gas detector tube (0.05 – 0.8 % by volume)
Suggested alarm levels Lo: 5 % LEL (2,000 ppm)
Hi: 10 % LEL (4,000 ppm)


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