AL2 + Water -> AL2O3 + H2
AL2O3 is alumina which is the raw form of aluminum. Basically, inside your reactor, you should have a catalyst that happen, something like aluminum hydroxyde for a final result of aluminum oxide and H2 in gas form. The vapor that smell a caustic vapor from the solution that contain sodium hydroxide and got a very high pH, so to remove these vapor, just pass your gas to a bubbler with something to neutralize (water + acide, like vinegar or Hcl) the sodium hydroxide, and you should have no more NaOH vapor. Be sure to check the pH of you're bubbler.