All three indexes are shown as a % of a recommended limit so they can be compared on one scale: CNS% is already a % of the NOAA single-exposure limit; OTU is shown as a % of a commonly-cited 300 OTU/day reference; ESOT is shown as a % of the DMAC 35 Rev 1 660 single-exposure limit. The vertical dashed line marks surfacing. CNS% decays after surfacing (~90 min half-time); OTU is shown flat since it has no recovery function, only a daily limit; ESOT decays after surfacing using its own recovery model, which recovers more slowly the longer the dive was.
OTU and ESOT are two competing measures of pulmonary toxicity — DMAC 35 Rev 1 adopted ESOT in place of the older UPTD/OTU. Note that DMAC does not score air-only dives at all, but here it is computed for any PO2.