Hydrogen as a fuel for internal combustion engines (ICE) is seen as an alternative way to conquer the threat of climate warming in the transport sector. With its broad range of ignition behavior and its very fast burn rate it offers some good potential as well. Currently this fuel in a gas phase is handled compared to CH4 in gas engine looking on storage and ignition system—with adaptation in flow rates and leak tightness. Whether hydrogen is injected indirectly to the intake system whether directly to the combustion cell there are at least two problems caused by that fuel. In the first step hydrogen gets via piston, cylinder and piston rings into the crank case and forms concentrations likely to cause ignition in the crank case (lambda < 10). In the second step in combustion of hydrogens comes with a far higher water concentration in the exhaust gas, which will get into the crankcase as well and where it can leave the gas phase forming liquid water touching the oil in the engine—higher water content than permissible. Hengst has proven in the past, for the use in passenger car vehicle, that an active crank case ventilation system can be a possibility to solve this problem. The ability to convey gas out of the crankcase with an electrically driven system offers the ability to activate an aeration of the crankcase air to dilute the natural blow by flow with fresh air and by this to minder the concentration of hydrogen in the crankcase atmosphere. The dilution can be done with a critical nozzle in combination with a check valve function, which is adapted to the Hengst Blue.tron system and to the engine itself. The fresh air flushing through the crank case can not only drive down the concentration of hydrogen but can also catch the water in the expanding atmosphere. Engine dyno tests with a combination of Hengst disc separators and Hengst aeration valves proves the behavior on hydrogen use. Engines of different sizes—coming from passenger size up to heavy duty commercial vehicle size—are currently tested for the behavior about active separation and aeration of the crank case. Hydrogen as well as water content have been lowered towards lower temperatures and towards higher loads.