We have been doing concealment wrong

[Minous]

When running into any type of concealment we have been denying AoO's (IE Obscuring mist). However you are only denied AoO's when concealment is >=%50

[mikem91]

you're right. PRD 197:

Concealment Miss Chance: Concealment gives the
subject of a successful attack a 20% chance that the
attacker missed because of the concealment. Make the
attack normally—if the attacker hits, the defender must
make a miss chance d% roll to avoid being struck. Multiple
concealment conditions do not stack.

Concealment and Stealth Checks: You can use
concealment to make a Stealth check. Without concealment,
you usually need cover to make a Stealth check.

Total Concealment: If you have line of effect to a
target but not line of sight, he is considered to have total
concealment from you. You can’t attack an opponent that
has total concealment, though you can attack into a square
that you think he occupies. A successful attack into a
square occupied by an enemy with total concealment has a
50% miss chance (instead of the normal 20% miss chance
for an opponent with concealment).

You can’t execute an attack of opportunity against an
opponent with total concealment, even if you know what
square or squares the opponent occupies.