% LEL Calculator for Gas Detectors
Convert between ppm, % volume and % LEL for flammable gas detectors, and check typical alarm levels.
- % LEL = ppm ÷ (LEL % × 10,000) × 100
LEL Conversion
1 % vol = 10,000 ppm
LEL values shown are as listed in IEC 60079-20-1; other references (for example NIOSH) give slightly different values, such as 5 % for methane. Use the value your gas detector is calibrated to.
Worked example
5000 ppm (0.5 % vol) of methane with LEL 4.4 % is 11.4 % LEL; with the older 5 % LEL it reads 10 % LEL.
Frequently Asked Questions
What is LEL?
Lower explosive limit: the lowest concentration of a flammable gas in air that can ignite.
What is 100 % LEL for methane?
4.4 % volume (44,000 ppm) per IEC 60079-20-1, 5 % in older references.
What are typical gas detector alarm levels?
Commonly 10 % LEL low alarm and 20 % LEL high alarm, but follow your site standard.
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