When the D4i tissue saturation warning symbol is shown, then any one of the nitrogen tissue compartment saturations (slow or fast) is 75% or above. The idea is to warn the diver if tissue saturation is “relatively close” to maximum.
The tissue level warning comes when any tissue is 50% from its allowed surfacing pressure. It does not mean anything during a dive, but rather when on surface, it is a recommendation not to dive until set warning becomes off. E.g. it is recommended to consider not diving again until the tissue becomes low enough.
TOP 10 CONTRIBUTOR answered 2 days ago Beatrice_from_Suunto