LEL stands for the Lower Explosive Limit of a gas. It is the minimal concentration of the gas required for the gas to ignite. It is normally expressed as a percentage of the total air. PPM stands for parts per million. It also is a measure of concentration, though it is often provided by gas meters.

Pencil on calculator
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Step 1

Multiply the LEL percentage number by 10,000 to get PPM.

Step 2

To convert from PPM to an LEL percentage, divide the PPM by 10,000.

Step 3

For example, ethylene has an LEL of 2.7 percent. Multiplying this by 10,000 gives 27,000 PPM as the lower explosive limit, as it would be displayed on a gas meter.