A blend valve assembly including a plurality of ports, a stator having at least one fluid flow path defined therein that extends between at least one port of the plurality of ports in communication with the primary fluid media and at least one port of the plurality of ports in communication with an intake of a testing device, and a rotor comprising at least one fluid flow path defined therein. The rotor is movable between a series of positions such that the blend valve assembly is operable to provide the intake of the testing device with only the primary fluid media and to provide the intake of the testing device with a blend of the primary fluid media and the secondary fluid media.