because hydrogen is flammable so you have to be very
Hydrogen is explosive, helium not.
helium is a safer choice than hydrogen because helium is very reactive with oxygen while hydrogen is not
Hydrogen is extremely flammable, helium is not flammable at all.
Helium is not reactive, cannot explode.
helium is 2 times heavier than hydrogen helium is not so reactive , hydrogen is extremely flamable unlike helium.
Yes, because helium doesn't react, burn or explode.
Generally speaking, helium is safer, as it is an inert gas, but Hydrogen is cheaper to make and is lighter.
Because helium is an inert gas and won't burn (unlike hydrogen). See: Hindenburg.
Heavier but safer. Look what happened to the Hindenburg:(
because hydrogen is flammable. in fact, forget that, its down right explosive.
Helium is inert. Will not burn like hydrogen does so well.
The reason why helium is used instead of hydrogen in airships is that it's also light in weight, and the reason why hydrogen is replaced is because of its reaction with oxygen.
Although Hydrogen is one on the element scale, Helium is a preferred gas to use in balloons because it is a safer (not flammable) gas than hydrogen.
Hydrogen is extremely flammable and helium is safer.
Hydrogen is much more likely to ignite and cause a massive fire than helium (see Hindenburg disaster). Because Helium is much more stable than Hydrogen is is used in airships because it is a lot safer.