Question

as we know that hot air balloon floots by the hot air of the flame burning inside. wont the balloon catch fire?

Answer 1

The material of a hot air balloon is carefully selected to keep the same thing in mind. The balloon does not catch fire as the material it is made out of has a melting, ignition point quite higher than the temperature at which the fire burns or the inside air is. So, the balloon is able to sustain such a fire.