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[Typical O2 consumption = 1 litre/min.]

The graph shows how gas consumption (litres/min) in conventional open circuit air diving increases dramatically with depth. In comparison the Inspiration Closed Circuit delivers only the oxygen required by the diver, which is the same mass independent of depth and so consumption remains constant. For the average person this only amounts to about one litre per minute!
With the Inspiration gas consumption is determined by the quantity of oxygen that you metabolise, and this quantity remains the same at all depths. Therefore, when calculating gas duration you do not have to multiply the volume consumed by the ambient pressure as you do with open-circuit.
This means at 40m the Inspiration is at least 100 times more gas efficient than open circuit, or to put it another way, the Inspiration's 3 litre oxygen cylinder can give the same duration as 20 x 12 litre, 232 bar cylinders at 30m.