Gas Monitor LEL in Low Oxygen Environments

Written By Cameron Hunter

You may need a gas monitor to test for flammable gases (measured as %LEL) in low oxygen atmospheres if purging gas lines, tanks or vessels with nitrogen, argon or carbon dioxide. You have 2 basic options when selecting a portable monitor that has a sensor for flammable gas; CatEX or InfraRed (IR)

Option 1: Catalytic bead EX (catEX) sensors

The most common LEL sensor used in portable gas monitors is the catEX sensor. This sensor needs more than 10% of oxygen in the air to function accurately. A catEX sensor is not suitable for inert atmospheres.

Option 2: InfraRed (IR) sensors

An IR sensor can detect most flammable gases in inert atmospheres… but beware

·         IR will not detect acetylene or hydrogen gas

·         Must apply correction factor for the target flammable gas or results may be incorrect by more than 10X

For more detailed information, see Industrial Scientific article: https://www.indsci.com/en/blog/wireless-gas-detectors-for-confined-space-entries

Cameron Hunter
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