This window specifies the arrangement of the flowmeter, animal chamber, scrubbers, and gas analyzer(s) -- in turn, this arrangement is crucial to determining the conversion equation for either oxygen consumption or CO2 production.
For VO2 Modes 3 and 5 and Mask Modes 1 and 3, and for CO2 Mode 2 and Mask Mode 1, the positions of the flow meter and gas analyzer can be 'flipped' with no effect. In other words, either the gas analyzer or the flow meter can be last in the 'chain'.
The plumbing arrangement shown for O2 Mask Modes 4 and 5, CO2 Mode 4 (measuring flow rate on undried gas) is not recommended except at low temperatures or if you are sure relative humidity in the gas stream is low.
For similar reasons, the plumbing arrangement shown for CO2 Mask Mode 3 (measuring CO2 concentration in undried gas) is not recommended.