>>14106541>Prove that hydrogen can burn when there's no other gas presentPutting aside the obvious answer 'fusion' for a moment, flammability means that stuff is flammable in an environment that provides an oxidizing agent.
Even then there need to be the right conditions at hand (lower-/upper-flammability limit, temperature,...) but let's ignore these for the sake of just defining flammability.
Hydrogen is flammable because it can react with the oxygen in the air.
Nitrogen is not flammable because it will not react with any oxidant.
Again, the definition of flammability already includes the presence of an oxidizing agent.
