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H2 Gas and its Sensor

Intro to Hydrogen

Hydrogen gas is a chemical element comprised of two hydrogen atoms with the formula H₂. In its pure form, hydrogen is a colorless, odorless, and tasteless gas. It is nonpoisonous but extremely flammable and requires careful handling to ensure safety. Hydrogen is the most abundant element in the universe, accounting for 90 percent of the universe by weight. However, it is rarely found in its pure form on Earth as it readily combines with other elements. Hydrogen is commonly used in various industrial processes, including refining petroleum, producing chemicals, and as a potential clean fuel source. 

Hydrogen gas is extremely light, with a density of 0.08988 grams per liter at standard pressure. This property makes it valuable in applications such as fuel cells and as a lifting gas in balloons and airships. Despite its lightness and abundance, the safe handling of hydrogen is crucial due to its flammability. 

Industrial hydrogen production is significant, with numerous large-scale plants worldwide. Hydrogen is often produced through methods like steam methane reforming and electrolysis, processes that involve splitting water molecules to extract hydrogen gas. 

Caractéristiques des gaz

  • Incolore 
  • Sans odeur 
  • Sans goût 
  • Extremely Flammable 
  • Lightest of all elements. 
  • Hydrogen in air is flammable at concentrations between 4% and 75% by volume (for comparison, methane is flammable in air only in a proportion between 4.4% and 17% by volume) 
  • Hydrogen gas consists of H2 molecules: each molecule is made up of two hydrogen atoms bound together. 
  • Henry Cavendish discovered it in mid-18th century and described it as “inflammable air.”  
  • The most abundant element in the universe equating to  approximately 75% of all normal matter.  
  • Hydrogen atoms have just one proton and one electron.  
  • Hydrogen is a diatomic gas having the formula H2.  
  • The term hydrogen comes from the Greek for “water former.”  
  • CAS 1333-74-0 
icône ghs inflammable - exemples : oxydes d'azote, solutions concentrées d'ammoniac, ammoniac anhydre
icon ghs toxique - exemples : l'acide nitrique qui peut dissoudre les métaux alcalins et endommager les voies respiratoires des travailleurs ainsi que le chlorure d'ammonium.
SGH corrosif SIMDUT - exemples : acides sulfurique et nitrique, y compris l'hydroxyde d'ammonium qui est un gaz corrosif.

Hydrogen Color Spectrum 

Green Hydrogen is produced with no harmful greenhouse gas emissions and is made by using electricity from surplus renewable energy sources, such as solar and wind power. This surplus electricity splits water into hydrogen and oxygen, emitting zero carbon dioxide in electrolysis. Green hydrogen is ideal due to its environmentally friendly nature, but it currently only makes up a small percentage of the overall hydrogen available. This is because of the high cost of production and the limited amount of surplus renewable energy. 

Blue hydrogen, also known as decarbonised hydrogen, is primarily produced from natural gas using a process called steam reforming (either by Steam Methane Reforming (SMR) or Auto Thermal Reforming (ATR)). When natural gas and very hot steam are mixed together, hydrogen and carbon dioxide get separated. The carbon dioxide is then captured and stored safely, but the hydrogen is transported as a fuel gas.  

Grey hydrogen is produced using the same process as Blue Hydrogen: steam reforming. Instead of capturing the carbon dioxide it is released into the atmosphere. 


Black hydrogen is produced using black coal as the feedstock, the harmful greenhouse gases are released in the atmosphere. 

Brown hydrogen is produced using brown coal as the feedstock, the harmful greenhouse gases are released in the atmosphere. 

Pink Hydrogen is produced using electricity generated by nuclear energy.  

Turquoise hydrogen is sometimes referred to as pre-combustion hydrogen, produced using a technique known as pyrolysis to create hydrogen and solid carbon.  

Yellow Hydrogen is produced using electricity generated by solar energy. 

White hydrogen is a natural form of Hydrogen that occurs within the earth's geology. It is captured by using techniques such as fracking. 

Industrial H2 detection, hazards and sources

  • While hydrogen performs well as a fuel, it presents a much greater explosion hazard than many other liquid and gas fuels. This is for two reasons. Firstly, hydrogen is much more difficult to contain than other gases. Hydrogen gas consists of H2 molecules: each molecule is made up of two hydrogen atoms bound together. This makes H2 the smallest molecule in the universe. Hydrogen gas is therefore prone to leaking out of containment.  
  • In addition to this, hydrogen is extremely flammable. Hydrogen in air is flammable at concentrations between 4% and 75% by volume (for comparison, methane is flammable in air only in a proportion between 4.4% and 17% by volume). The amount of energy required to ignite a hydrogen/air mixture is also much lower than for other fuels. The minimum amount of energy required to ignite a mixture of hydrogen and air is just 0.017 mJ. In contrast, the minimum ignition energy for hydrocarbon fuel gases is much higher, at around 0.3 mJ for methane/air or propane/air mixtures. The result is that hydrogen leaks are common, and even very small hydrogen leaks can be relatively easily ignited. 


It estimates that Hydrogen Gas leakage rates could reach up to 5.6% by 2050 when hydrogen is being used more widely.


Scénarios à haut risque

  • Chemical Plants using hydrogen for the production of ammonia and methanol pose high risks of hydrogen leakage due to its high flammability. 
  • Petroleum Refineries are also at great risk of hydrogen leaks, as Hydrogen is essential in refining processes, particularly in hydrocracking and desulfurization. Gas detectors can measure the levels of hydrogen in the high-pressure hydrogen systems in refineries. 
  • Hydrogen Fuelling Stations: As the demand for cleaner fuel increases, we will see more Hydrogen Fueling Stations which also brings the risks of poorly managed stations. These stations need connected safety systems and gas detectors to detect and mitigate leaks, and proper emergency protocols to handle potential fires or explosions. 
  • Storage Facilities: Large-scale storage of hydrogen, whether as a compressed gas or cryogenic liquid, presents hazards due to its flammability and the potential for leaks. Storage tanks must be designed to withstand high pressures and extreme temperatures, and facilities must have measures in place to quickly disperse any hydrogen that escapes to prevent accumulation and potential ignition (AIChE) (NREL Home) . 
  • Transportation: Hydrogen is transported in high-pressure pipelines and cryogenic tankers. The integrity of these transportation systems is critical to prevent leaks and ruptures, which can lead to fires or explosions. Safety measures include rigorous inspection protocols and maintenance schedules to ensure the pipelines and tankers remain secure (NREL Home) . 

H2 Sensor Info*

Type: Electrochemical
Range: 0–40,000 ppm
Sensitivity Range: 1 nA/ppm ± 0.5 nA/ppm

*not available in all regions


Niveaux d'alarme par défaut

Low Alarm: 4,000 ppm
High Alarm: 8,000 ppm

Questions about the detection of H2?


Applications et considérations particulières

  • Stored: Hydrogen gas detection is crucial in environments where hydrogen is used or stored, such as refineries, chemical plants, and laboratories. Considerations should be made for potential sources of hydrogen generation, such as electrolysis, steam reforming, and biomass gasification. 
  • Low Viscosity: Hydrogen poses several industrial hazards due to its unique properties. Its ability to diffuse through some solid materials can lead to embrittlement and system failures. As the smallest of all molecules, hydrogen has a very low viscosity, making it difficult to prevent leaks. Its high buoyancy means that, when released, hydrogen rises and may collect at high levels. 
  • Highly Flammable: Hydrogen's high flammability range and very low ignition energy (0.02mJ, which is 1/10th that of methane) mean even small sparks, such as those from clothing, can cause ignition, leading to explosions.  
  • Invisible: Hydrogen burns with an invisible flame in daylight, making detection difficult without added color. Spontaneous ignition of sudden releases has been observed, though the mechanism remains unknown. The rapid burning rate and flame speed result in higher explosion pressures and rates of pressure rise, making explosive mixtures more prone to detonation compared to other common fuel gases. 
  • Liquid Form: Liquified hydrogen, often transported at -253°C, can cause severe burns upon contact, and the vaporized gas may burn or explode. 

Health Risks and Handling of H2

0 - 0,5 ppm
No significant health effects; hydrogen is naturally present in the air at trace levels.
0,6 - 23 ppm
No significant health effects; concentrations within this range are still considered very low and safe for exposure.
24 - 29 ppm
No significant health effects; hydrogen at this concentration remains very low and does not pose a health risk.
30 - 49 ppm
No significant health effects; these concentrations are still low and do not pose a health risk.
50 - 71 ppm
No significant health effects; concentrations are still within a range that is considered safe.
72 - 139 ppm
No significant health effects; these concentrations are still not harmful.
140 - 499 ppm
No significant health effects; still within safe exposure limits.
500 - 1499 ppm
No significant health effects; hydrogen is non-toxic and these levels are generally considered safe.
1500 - 2499 ppm
No significant health effects; hydrogen is non-toxic, and this concentration is not typically hazardous.
2500 - 4500 ppm
No significant health effects; while hydrogen is non-toxic, care should be taken to avoid displacement of oxygen.
5000ppm +
At very high concentrations, hydrogen can displace oxygen in the air, leading to a risk of asphyxiation. Symptoms of asphyxiation include dizziness, headache, shortness of breath, unconsciousness, and potentially death if exposure continues without intervention.
H2 first aid
  • Inhalation: Remove to fresh air and keep at rest in a position comfortable for breathing. If not breathing, give artificial respiration. If breathing, trained personnel should give oxygen. Call a physician. 
  • Skin Contact: Adverse effects not expected from this product (unless liquified). 
  • Eye Contact: Immediately flush eyes thoroughly with water for at least 15 minutes. Hold the eyelids open and away from the eyeballs to ensure that all surfaces are flushed thoroughly. Get immediate medical attention. 

H2 dangers
  • Evacuate the area immediately and alert nearby personnel. 
  • Prevent ignition sources, including open flames, sparks, and electrical equipment. 
  • Ventilate the area to disperse the hydrogen gas safely. 


Les gaz combustibles et leur détection

Les gaz combustibles sont l'un des plus grands risques auxquels une installation industrielle peut être confrontée. Ce livre blanc complet couvre les bases et les dernières avancées en matière de technologie de détection des LIE. 

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