Everybody agrees that the accidental only applies for the duration of the bar and for the octave in which it appears. What I'm not totally sure of is the following...You can write the same pitch in the same octave in either the treble or bass clef, at least for pitches fairly close to middle C. I don't know whether an accidental on a B below middle C on the bass clef applies to a subsequent B below middle C written below the treble clef with a ledger line. I would guess that it does, but I've never seen it come up. Also don't know whether if the two staves temporarily use the same clef, both treble or both bass, whether accidentals in one staff apply to the same pitch on the other staff.