Concentrating on a Supernatural Ability

[Albinobear]

Planar Bubble is a Supernatural Ability. Faiths of Eberron says it requires concentration. The PHB says supernatural abilities require no concentration. I know that FoE would overrule this, but then what kind of action does it make it?

It would definitely be a standard to start, but what would the concentration be?

I would assume a free action, because it using a Su ability doesn't provoke attacks of opportunity

In general, if an action wouldn’t normally provoke an attack
of opportunity, you need not make a Concentration check to avoid
being distracted.

What kind of action is it to concentrate on a Supernatural Ability?

[tyckspoon]

It would either go under 'Concentrate to maintain a spell' or 'Use a Supernatural Ability', both of which are non-provoking Standard actions.

[Jack_Simth]

The PHB says supernatural abilities require no concentration. Not quite right. It says supernatural abilities require no concentration checks. It's still the standard action to concentrate on the thing... you just don't lose it if someone drops 1,000 damage on you (unless that removes your ability to act in the next round, of course).