100% means 100 parts out of 100:

- 100% of anything means it is all the same thing

10%, means 10 parts out of 100, (1/10^{th} of 100), so therefore its 90% something else.

- 1% means 1 part out of a 100

Eventually we go down to 0.1%, 0.01%, 0.001%, but these numbers get kind of cumbersome, so it becomes convenient to change scale.

100% also means 1 million out of a million

Therefore, 10% is the same as 100,000 parts of a million (ppm).

1% is the same as 10,000 parts per million.

This one is important, 1% = 10,000 ppm.

1% = 10,000 ppm

- 0.1% = 1000 ppm
- 0.01% = 100 ppm
- 0.001% = 10 ppm
- 0.0001% = 1 ppm = 1000 ppb
- 0.000001% = 0.1 ppm = 100 ppb
- 0.0000001% = 0.01ppm = 10 ppb
- 0.00000001% = 0.001 ppm = 1 ppb = 1000 ppt (parts per trillion)

LEL (Lower Explosion Limit) to % to ppm examples:

- 100% LEL = 5% methane = 50,000 ppm methane
- 10% LEL = 0.5% methane = 5000 ppm methane
- 1% LEL = 0.05% methane = 500 ppm methane

Link to LEL Conversions

Mike DexterShould a customer send a request and only mentions the % LEL level then you must either quote both EU and Global standards.

Example: 2.5% CH4 vs 2.2% CH4

If unsure then please ask the customer to confirm the % VOLUME they require or refer them to the instrument manufacturer.

Thanks