Hydro does not create any deadly gasses, H2o as you know is water., hydrogen and oxygen are the two components that make water. So burning hydrogen only emits water vapors when it is burned as it mixes with the natural oxygen in the air. Most Hyogen vehical rely on storage tanks of Hydrogen to fuel the vehicle, The cost of recharging the system and available recharging station are the main downside of using Hydrogen. However, I have a self generating Hydrogen generator that creates Hydrogen as you drive, using your engine to create the electricity through a series of alternators to charge the generator and make Hydrogen as you drive. The more amps the more Hydrogen you get. Consume as you drive rather than store. The ideal way is to not have storage of combustable gasses, rather use it as you drive and just add more water as the water level gets lower.