Disclosed is a mixing chamber apparatus suitable for high-volume sampling (HVS) application. The mixing chamber apparatus includes, among other elements, inlet and outlet manifolds, a mixing chamber, and a tubing manifold for the introduction of clean, turbulent air into the mixing chamber. The inlet manifold defines a plurality of vapor ports that can be in fluid communication with one or more vapor sources to be sampled and mixed within the mixing chamber. Also described herein is a baffled mixing system that can be used alone or in combination with the disclosed mixing chamber apparatus.