Incapacitated doesn't appear to be a game-term described exactly in the mechanics.
Some conditions which may be applied, taken from the SRD:
The character cannot see. He takes a -2 penalty to Armor Class (read: DV), loses his Dexterity bonus to AC (if any) (read: DV), moves at half speed, and takes a -4 penalty on Search checks and on most Strength- and Dexterity-based skill checks. All checks and activities that rely on vision (such as reading and Spot checks) automatically fail. All opponents are considered to have total concealment (50% miss chance) to the blinded character. Characters who remain blinded for a long time grow accustomed to these drawbacks and can overcome some of them.
The creature is unable to act normally. A dazed creature can take no actions, but has no penalty to AC (read: DV).
A dazed condition typically lasts 1 round.
The creature is unable to see well because of overstimulation of the eyes. A dazzled creature takes a -1 penalty on attack rolls, Search checks, and Spot checks.
A deafened character cannot hear. She takes a -4 penalty on initiative checks, automatically fails Listen checks, and has a 20% chance of spell failure when casting spells with verbal components. Characters who remain deafened for a long time grow accustomed to these drawbacks and can overcome some of them.
Depending on their size, creatures can be knocked down by winds of high velocity. Creatures on the ground are knocked prone by the force of the wind. Flying creatures are instead blown back 1d6 × 10 feet.
A stunned creature drops everything held, can’t take actions, takes a -2 penalty to AC (read: DV), and loses his Dexterity bonus to AC (if any) (read: DV).
I would also have the PCs make a Terror of the Unknown check [313, AE], if they have never been exposed to explosive attacks as these.