parts per million | Energy Glossary

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parts per million

1. n. []

A unit of concentration, frequently abbreviated to ppm. For solid and liquid concentrations, ppm refers to weight (mass) units. For example,

Note that the relationship of ppm to weight percentage is 10,000 ppm = 1 wt%. For gases, ppm refers to volume (or mole) units. For example, H2S in an air sample may be 10 ppm (both by volume and by moles).

See: dissolved solidsepmLC50milligrams per liter