NOVELTY - Electrochemical cell (C1) (100) comprises: a pair of bipolar plates and membrane electrode assembly located between pair of bipolar plates, where the assembly comprises anode (110), cathode (120) and proton exchange membrane (150, 160) disposed between them; a first seal defining high pressure zone, where first seal is located between bipolar plates and configured to contain first fluid within high pressure zone; and a second seal defining intermediate pressure zone, where second seal is located between bipolar plates and configured to contain second fluid within intermediate pressure zone.    USE - The electrochemical cell is useful to form multi-stage electrochemical hydrogen compressor or a single-stage electrochemical hydrogen compressor.    ADVANTAGE - The electrochemical cell: has a cascade seal configuration to enable the collection and recycling of hydrogen leaked from the cell, thus it is efficient in preventing or reducing hydrogen leakage, and is safe and energy efficient; exhibits improved tuning capability, electrical conductivity, corrosion resistance and serviceability; and can be manufactured in cost effective manner.    DETAILED DESCRIPTION - Electrochemical cell (C1) (100) comprises: a pair of bipolar plates and a membrane electrode assembly located between the pair of bipolar plates, where the membrane electrode assembly comprises an anode (110), a cathode (120), and a proton exchange membrane (150, 160) disposed between them; a first seal defining a high pressure zone, where the first seal is located between the bipolar plates and configured to contain a first fluid within the high pressure zone; and a second seal defining an intermediate pressure zone, where the second seal is located between the bipolar plates and configured to contain a second fluid within the intermediate pressure zone, and the first seal is configured to leak the first fluid into the intermediate pressure zone when the first seal unseats. INDEPENDENT CLAIMS are also included for:    (1) an electrochemical cell (C2), comprising: the pair of bipolar plates and the membrane electrode assembly located between the pair of bipolar plates; a high pressure zone that is located between the bipolar plates and contains the first fluid; an intermediate pressure zone that is located between the bipolar plates and contains the second fluid; and a low pressure zone containing the third fluid, where the electrochemical cell (C2) is configured to transition between a first configuration, a second configuration and a third configuration based on at least one of a closing force applied to the bipolar plates or an opening force produced by a pressure of at least one of the first fluid, second fluid or third fluid; and    (2) an electrochemical cell (C3) comprising: the pair of bipolar plates and the membrane electrode assembly located between the pair of bipolar plates; and a first cascade seal configuration between the pair of bipolar plates, where each bipolar plate comprises at least two components, and a second cascade seal configuration between the two components.    DESCRIPTION OF DRAWING(S) - The figure shows a side view of a part of the electrochemical cell.    Electrochemical cell (100)    Anode (110)    Cathode (120)    Proton exchange membrane (130)    Bipolar plates (150, 160)