Which gas is formed when a hydrogen bomb is detonated?

hydrogen isotopes are fused to form helium

When a hydrogen bomb, also known as a thermonuclear bomb, is detonated, the primary source of energy comes from the fusion of hydrogen isotopes. The hydrogen bomb uses a two-stage process: the first stage involves a conventional fission bomb (usually fueled with uranium or plutonium) to create the conditions necessary for the fusion reaction to occur.

During the fusion stage, the isotopes of hydrogen, specifically deuterium and tritium, undergo a nuclear reaction, fusing together to form helium. This fusion reaction releases a tremendous amount of energy in the form of an extremely high-temperature plasma.

So, when a hydrogen bomb is detonated, the primary gas formed is helium. The helium gas is a product of the fusion reaction, and its release signifies the immense energy released during the explosion.