Is Hydrogen Flammable?

Hydrogen is the first element on the periodic table with one proton and one electron. This also makes it the lightest element on the periodic table with a weight of just 1.0079 amu (atomic mass units). It's also the most abundant element in the universe.
Read more about the importance of hydrogen.

Hydrogen is also highly flammable and will easily combust or explode even at low concentrations.

Properties of Hydrogen

Hydrogen has one proton and one electron in its nucleus. The most common isotope of hydrogen has no neutrons.

This makes hydrogen one of the best elements at forming covalent bonds with other molecules and elements. In fact, it can form a covalent bond with almost any element on the periodic table because of its single proton and electron.

This also means that single atoms of hydrogen are extremely rare. It commonly forms hydrogen gas, which is a diatomic form of hydrogen (H2).

Under normal temperature and pressure conditions of Earth, hydrogen has no smell, is nontoxic, tasteless, colorless and nonmetallic. Hydrogen has a density of 0.89 g/L (less dense than air), and it has a melting point of about -259 °C and a boiling point of about -252.9 °C.

Is Hydrogen Flammable?

So, the big question: Is hydrogen flammable? The short answer is yes it is highly flammable, but there are a few things to clear up with this answer.

When it's said that hydrogen is flammable, it doesn't mean the elemental form of hydrogen. It's the diatomic hydrogen gas that is extremely flammable. Many flammable substances have to be at a high concentration in order to actually combust or catch fire, but that's not the case with hydrogen. Hydrogen will combust at concentrations as low as 4 percent up to 75 percent.

The reaction for this combustion is:

2H2(Gas) + O2 (Gas) = 2H2O (Liquid) + 572 kJ energy (286kJ/mol H2)

Explosions and combustion of hydrogen can occur with a simple spark and increased heat. However, it's also been seen to combust when exposed to sunlight and even very minor increases in temperature because of its highly reactive nature.

Hydrogen Fuel

Despite the highly explosive and flammable quality of hydrogen gas, people have found many uses for hydrogen that are directly related to its flammability.

Perhaps the most common is hydrogen fuel and fuel cells. Hydrogen fuel combines hydrogen and oxygen in order to create electricity and hydrogen power.

Hydrogen fuel is exciting since it is a "clean" source of energy that only produces water and energy when reacted (as you can see in the combustion equation above). Other fuel sources like gas and oil produce harmful gases and emissions that are harmful to the environment. People have found uses to bring hydrogen power to homes, cars, portable energy sources and more.
Read more about hydrogen fuel vs fossil fuel.

Other Uses for Hydrogen

Hydrogen gas is also used in many industrial and manufacturing processes especially those that use petroleum as well as ones that require hydrogenation of products like hydrogenated oils.

Other common uses for hydrogen include:

  • Use as a coolant
  • Welding applications
  • Previous use in air balloons and airships

Scientists discovered the power of hydrogen combustion and the other properties of hydrogen and used that information in order to create hydrogen bombs, which are also called fusion bombs. These bombs force multiple hydrogen nuclei to combine into helium atoms in a process called fusion.

This occurs at high temperatures and results in a massive output of energy, which is known as an explosion. Hydrogen is used in these fusion bombs since they're very light and have the least amount of resistance of joining nuclei (this doesn't decrease the power of the hydrogen bomb, though).


About the Author

Elliot Walsh holds a B.S in Cell and Developmental Biology and a B.A in English Literature from the University of Rochester. He's worked in multiple academic research labs, at a pharmaceutical company, as a TA for chemistry, and as a tutor in STEM subjects. He's currently working full-time as a content writer and editor.