Explosion limit of blast furnace gas is $37$ to $71\%$ gas in gas$-$air mixture. It means that the blast furnace gas will explode when burnt in a confined space, if its concentration in the gas$-$air mixture is $\_\_\_\_\_\_\_\_\_$ percent.

$<37\%$

$>71\%$

In between $37$ & $71\%$

None of these