Whenever a saline hydride `(NaH or CaH_(2))` reacts with water, the reaction is so highly exothermic that the hydrogen evolved catched fire. For example,
`NaH(s)+H_(2)O(aq) to NaOH(aq)+H_(2)(g)+"heat"`
`CaH_(2)(s)+2H_(2)O(aq) to Ca(OH)_(2)(aq)+2H_(2)(g)+"heat"`
`CO_(2)` which is normally used as fire extinguisher cannot be used in this case beacuse it will react with the hydroxide formed in the reaction to form a carbonate. This will increase the rate of the forward reaction in which heat is evolved.
`2NaOH(aq)+CO_(2)(g) to Na_(2)CO_(3)(aq)+H_(2)(aq).`