MPE, or Multi-Phase Extraction, is a traditional extraction system that uses a high vacuum air pump. This air pump can achieve very low pressures, ideal for extraction under phreatic conditions. The term Three-Phase Extraction is also used, as a mixture is often extracted from water, product (non-aqueous phase liquid layer, NAPL) and soil vapour.

Other terms include high vacuum extraction, triple phase extraction, multiple phase extraction and dual phase extraction. The term used often refers to the intended goal: extracting air + product could for example be described as “Two-Phase Extraction”.