Recently I received some nice pictures of the Emerson MK6
Semi closed rebreather. This very early design from the 70's is little known
in Europe but was used for many years in de US army. The Emerson rebreather
was also called "the Green Death". De rebreather is a constant flow mixed
gas SCR. It uses a constant mass regulator and a needle valve to set
the flow. The manual says it is rated for 180 ft (55 mtr) with a premix of
32 % of oxygen resulting in a pO2 of 2,08 bar! The MK 6 was later to be
replaced b the MK15.