Molecular hydrogen
Hydrogen safety is related to the fundamental properties of the molecule. Hydrogen has the symbol H and atomic number 1. It forms a diatomic gas (H2) at standard conditions, which is also called molecular hydrogen. Molecular hydrogen is the lightest of all gases with a density 84 gH2/m3 at 15 °C and 1 bar(a). Due to its low density and high diffusivity, the gas disperses rapidly in the air. Since it is lighter than air, it will generally move upwards in space. Important properties of molecular hydrogen are summarized in the table below.
| Property | Value |
| Density at 15 °C and 1 bar(a) | 84 gH2/m3 |
| Melting point | -259.2 °C |
| Boiling point | -252.9 °C |
| Lower flammability limit | 4 %Vol |
| Upper flammability limit | 76 %Vol |
Environmental impact and risks
Hydrogen is not harmful to the environment. It does not damage the ozone layer and it is not directly a greenhouse gas (see, e.g., here). Its combustion generates only water as a byproduct which is an environmentally benign substance. Hydrogen does not have any adverse health effects. The main risks associated with the usage of hydrogen are fires and explosions. In comparison with other flammable gases, the range of concentrations in which a flammable or explosive mixture can occur is relatively high. Furthermore, the gas diffuses rapidly, which increases the risk of creating an explosive hydrogen-to-air mixture. Therefore, the risk management of hydrogen systems aims primarily at preventing the creation of an explosive mixture.
Measures improving hydrogen safety
There are several different measures that can be taken to manage these risks and ensure high hydrogen safety standards:
- Tightness of systems: tightness of the gas system is paramount for the prevention of air entering the system and creating an explosive atmosphere inside, as well as to prevent hydrogen from entering the surrounding atmosphere.
- Limiting leakage flows: limiting leakage flows when they occur greatly increases the safety of
the overall plant. - Adequate ventilation: sufficient air exchange will ensure that, in the unlikely event of a
hydrogen leakage, the probability of surpassing the lower explosion limit is low if ventilation is
running. - Avoid or reduce the probability of ignition: finally, to additionally increase safety, ignition
sources can be limited or reduced, e.g., by selecting adequate electronic components.
GRZ Technologies’ hydrogen storage and compression technology features different unique technical properties that make it even more safe than other hydrogen technology, more information can be found, for instance, in this article.