Gaseous Hydrogen Properties and Behaviors

Some basic properties and behaviors of gaseous hydrogen are highlighted on this page. For more information on hydrogen properties, see Hydrogen Compared with Other Fuels.

Introductory video here.

• Hydrogen is a gas at ambient conditions.
• It is the lightest molecule in the universe.
• It is 14 times lighter than air, so it rises at almost 20 meters per second (44 miles per hour) and disperses rapidly. This buoyancy is a built-in safety advantage in an outside environment.
• It is colorless, odorless, tasteless, and undetectable by human senses.
• It is non-toxic and non-poisonous.
• At high concentrations can be an asphyxiant.
• It is flammable and explosive over a wide range of concentrations, so it should be safely stored and used in an area that is free of heat, flames, and sparks.
• It has a very low ignition energy, that is, it can be easily ignited by a small spark.
• It is non-corrosive, but it can embrittle some metals (i.e., cause significant deterioration of the metal's mechanical properties) so it is important that any material in contact with hydrogen be specifically chosen for compatibility.

Figure 1. Relative Vapor Density