Hydrogen is colorless, odorless, tasteless, non-toxic, and non-poisonous. It’s also non-corrosive, but it can embrittle some metals. Hydrogen is the lightest and smallest element, and it is a gas under atmospheric conditions.
Hydrogen has a high energy content by weight, but not by volume, which is a particular challenge for storage. In order to store sufficient quantities of hydrogen gas, it’s compressed and stored at high pressures. For safety, hydrogen tanks are equipped with pressure relief devices that will prevent the pressures in the tanks from becoming too high.
Hydrogen is about 57 times lighter than gasoline vapor and 14 times lighter than air. This means that if it is released in an open environment, it will typically rise and disperse rapidly. This is a safety advantage in an outside environment. Poor venting may result in gathering hydrogen in compartment and spontaneous ignition and burn.