Here is image of the system:

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Clean air flows through the mixing chambeer. WHen a miniMFC is activated, some air goes into the olfactometer, through the miniMFC, into the vial, into the isolation valve (now opened), into the mixing chamber, mixes with the clean air stream.

Needle valve is necessary to increase impedance on the mixing chamber line. Must be adjusted (tightened) enough so that the miniMFCs can reach 100cc or so, but loose enough so that the Alicat MFC can still push 1000cc through the system.