What is LEL: The Key Metric of Combustible Gas Safety

Understanding Combustible Gases

A combustible gas is any gaseous substance that can ignite in the presence of a heat source and oxygen, potentially leading to an explosion. Common examples include methane, propane, hydrogen and iso-butane – all widely used in industrial processes. While these gases are essential for energy production and manufacturing, they also pose significant safety risks to personnel, equipment, and the environment.

From LEL to UEL: Defining the Explosive Range

To mitigate the risks associated with combustible gases, it’s crucial to understand their explosive range, which falls between the Lower Explosive Limit (LEL) and Upper Explosive Limit (UEL):

  • LEL (Lower Explosive Limit): The minimum concentration of a gas in air required for ignition. Below this level, the mixture is too “lean” to burn.
  • UEL (Upper Explosive Limit): The maximum concentration at which combustion is possible. Above this level, the mixture is too “rich” to sustain ignition.

Industries often use percentages of LEL to denote gas concentrations, rather than doing so by volume – this adds a dimension of risk degree to the metric. For example, if methane is present at 2.5%vol, this would equal 50% of its LEL (since the LEL for methane is 5%), which is normally enough to trigger a warning or counter measure.

Consequently, gas monitoring in industrial applications tends to focus on concentrations leading up to LEL, but in some gas-rich environments concentration could decrease from a mixture that is too rich to burn, towards the UEL threshold. Such situations are equally dangerous and warrant the same amount of caution as concentrations approaching the LEL.

The Combustion Triangle: How does an explosion occur?

For combustion to occur, all three elements must be present:

🛢️  Fuel (combustible gas)
💨 Oxygen (usually present in ambient air)
⚡ Ignition Source (a spark, flame, or heat source)

If any one of the elements is removed, combustion cannot occur. Several protection principles, outlined in the ATEX directive are based on this core dependency.

Safety Measures - Solutions by Gas Sense

In order to manage the potential hazards associated with accumulations of combustible gas concentrations, continuous monitoring is necessary. Despite advancements in materials, machinery, and containment methods, gas detectors remain a vital safety measure for identifying and defusing dangerous situations as they arise.

Combustible gas detector models by Gas Sense such as the GDPC ATEX Gas Detector, the GS-300 Non-Hazardous Area Gas Detector and the H-400 Residential Gas Detector offer dependable continuous monitoring solutions for a wide array of explosive gases in many applications – from heavy industry to residential.

The Gas Sense GDPC ATEX Gas Detector

Gas Sense gas detectors are compliant with relevant standards, offer excellent accuracy and durability, and minimizes costs in three key ways:

✅ Low initial investment helps keep project expenses down;

✅ Our modular product architecture ensures you do not overpay for features you don’t need;

✅ Advanced maintenance facilitation features such as our industry-leading TouchCal™ automated calibration and our SafeSwap™ solderless sensor replacement make sure everything goes smoothly in the field. Zero-calibration sensor options also available.

Explore the Gas Sense combustible gas detector line for everything from ATEX and SIL-compliant solutions to reliable domestic detectors.

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