Are hydrogen and helium and oxygen poisonous?

Answer 1

Oxygen can be toxic in hydro concentrations, but it is essential in lower concentrations. Neither helium nor hydrogen are toxic, but they can displace oxygen simply because they take up space and so can cause asphyxiation. Hydrogen is dangerous because it is highly flammable.

Answer 2

Hydrogen and helium are generally considered non-toxic since they don't react with our bodies and are not harmful when inhaled or ingested in small amounts. Oxygen, on the other hand, is essential for human life and is not toxic in normal concentrations. However, excessively high levels of oxygen (such as in pure oxygen environments) can be toxic and potentially cause harm.