Also for anyone interested, you are dealing with partial pressures of oxygen (PO2) with Nitrox. With 36% Nitrox mix (36% O2, 64% N, EAN36)you shouldn't be going below 28 m, since you don't want to exceed a PO2 of 1.4. (36% * 4 ATA = 144% or 1.44 PO2). Oxygen toxicity comes on without warning in most cases, and you convulse and typically drown. You want to stay between 0.16 and 1.6 (max!, hence the 1.4 PO2 guideline). There are some subtleties you can find out by researching Nitrox diving, or taking the course and certifying for Nitrox diving.