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H2 Gas and its Sensor

Intro to Hydrogen

Hydrogen (H₂) is a colorless, odorless, highly flammable gas widely used in industries including energy, refining and chemical manufacturing.

Because it cannot be detected by human senses and ignites easily over a wide range of concentrations, hydrogen presents a significant safety risk.

Reliable hydrogen gas detection is essential for identifying leaks early and helping protect workers, facilities and operations.

Hydrogen Gas Characteristics

  • Colorless 
  • Odorless 
  • Tasteless 
  • Extremely Flammable 
  • Flammable at concentrations between 4% and 75% by volume
  • Very low ignition energy
  • Lighter than air and prone to accumulation at height
icon ghs flammable - examples include nitrogen oxides, concentrated ammonia solutions, anhydrous ammonia
icon ghs toxic - examples include nitric acid which can dissolve alkali metals and cause harm to the respiratory tract of workers along with ammonium chloride
icon-ghs-compressed-gas-or-compressed-liquid
GHS corrosive WHMIS - examples include sulphuric and nitric acids including ammonium hydroxide is a corrosive gas
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Why Hydrogen Needs Dedicated Detection

Understanding hydrogen's unique properties is key to recognizing where leaks can occur, how quickly they can become hazardous, and why reliable gas detection is essential.

  • Difficult to contain:
    Hydrogen is the smallest molecule, making it more likely to escape through tiny leaks.

  • Wide flammable range: Hydrogen is flammable in air at concentrations between 4% and 75%, creating a broad range of ignition risk.

  • Extremely easy to ignite: Hydrogen requires very little energy to ignite: even a small static discharge can be enough.

  • Invisible flame:
    Hydrogen burns with a nearly invisible flame, making fires difficult to detect without specialized equipment.

 

A high-risk scenario based on hydrogen demand from the International Energy Agency (IEA) net-zero scenario (528 million tons [Mt] by 2050) (IEA 2021) could potentially lead to a 5.6 percent economy-wide leakage rate.

(Source: Columbia University Policy Paper)

High Risk Scenarios

  • Chemical Plants:  Hydrogen is a key feedstock in ammonia and methanol production. Because it's highly flammable and can easily escape through small openings, early leak detection is essential to keeping those processes running safely. 
  • Petroleum Refineries: Hydrogen is essential to refining processes, particularly hydrocracking and desulfurization, making reliable leak detection a key part of safe operations. Gas detectors can measure the levels of hydrogen in the high-pressure hydrogen systems in refineries. 
  • Hydrogen Fueling Stations: As the demand for cleaner fuel increases, more hydrogen fueling stations are coming online. 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: Hydrogen is stored at large scale as a compressed gas or cryogenic liquid. 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
Resolution: 400 ppm

H2 gas detection sensors
Default Alarm Levels

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

Blackline devices that can detect H2

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Special Applications and Considerations

  • 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

concentration
symptoms/effects
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.

Health Risks and Handling of H2

Hydrogen is non-toxic and poses no direct health risk through exposure at normal concentrations (0 - 2499 ppm).

The primary hazard at very high concentrations is oxygen displacement, which can lead to asphyxiation (2500ppm +).

H2 first aid
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
IF ACCIDENTALLY RELEASED
  • 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.

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Combustible Gas and its Detection

Combustible gases are one of the greatest risks an industrial facility can face. This comprehensive white paper covers the basics through to the latest advancements in LEL detection technology.

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