It is the lightest gas, leading to high leak potential and requiring high-pressure storage (up to ) or cryogenic cooling to

. As of , it has transitioned from a niche industrial chemical to a central pillar of global energy security and decarbonization strategies, particularly for "hard-to-abate" sectors like heavy industry and long-haul shipping. 1. Physical and Chemical Properties

When used in a fuel cell, its only byproducts are water vapor and heat. 2. Production "Color" Spectrum

It has a wide ignition range (4% to 75% in air), requiring specialized safety protocols for transportation and use.

Hydrogen is classified by its production method and carbon footprint: Hydrogen Gas - an overview | ScienceDirect Topics