To make permeation measurements, one side of the test film needs to have a zero oxygen atmosphere (100% nitrogen) while the other side has to have a high oxygen atmosphere. The high oxygen can be achieved by either initially opening the valves to the bottom side of the OxySense Permeation Chamber, open to the atmosphere (20.8% oxygen) or by flushing the bottom side of the chamber with 100% oxygen. The flow meter allows the control of the flow rate of the gases flowing to the each side of the chamber so that film inside the chamber being tested does not deflect due to the inflow of gas during the flushing process.