specify noxious fog resistance

spells/Air1.tex

@@ -21,6 +21,8 @@
 
     The air only covers \arabic{spelllevel} square -- enough for a doorway, or small tunnel.
     It dissipates after a couple of turns, or less if wind is present.
+
+    Casting the spell outdoors raises the \gls{tn} by 1, casting it on a windy day raises it by 3, and casting the spell in a storm raises the \gls{tn} by 5.
   }
 
 \spell{Bubble}% Name