EMB145 CAPT MOVED THE ACFT WITHOUT CLRNC; TO CLR RWY 24L AND PREVENT BLAST DAMAGE TO HIS ACFT; WHEN THE TWR CTLR ISSUED TKOF CLRNC TO A DC9 ON RWY 24L.

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WE WERE TOLD TO FIRST TAXI TO RWY 24L VIA RWY 28; TO HOLD SHORT OF RWY 24L. THEN THE CTLR TOLD US TO TAXI ACROSS RWY 24L TO HOLD SHORT OF RWY 24C. WHILE HOLDING SHORT OF RWY 24C; AND OUR TAIL JUTTING OUT INTO RWY 24L; CTLR TOLD A DC9 TO DEPART OFF RWY 24L. EVEN DC9 STARTED ASKING IF THEY WERE GOING TO BLAST US. RATHER THAN HAVE THRUST DAMAGE TO OUR TAIL FROM THE DC9; I MOVED UP SLIGHTLY; XING OVER THE RWY 24C HOLDING LINE; BUT WELL SHORT OF RWY 24C; AND BEHIND THE HOLD SHORT LINE OF RWY 24L ON TXWY Z. I AM JUST GLAD NOBODY WAS LNDG ON RWY 24L. OBSERVATIONS: 1) CTLR SHOULD NOT ISSUE A TKOF CLRNC FOR AN ACFT ON RWY 24L WHEN THEY ARE ALSO HAVING AN ACFT HOLD ON TXWY Z; HOLDING SHORT OF RWY 24C. UNLESS YOU ARE A C150; YOU ARE GOING TO BE ON RWY 24L PAVEMENT WHILE ON TXWY Z; HOLDING SHORT OF RWY 24C. 2) ON TXWY Z; THE PRESENT RWY 24L HOLDING LINE (GOING E ON TXWY Z) SHOULD BE THE W HOLDING LINE FOR RWY 24C. THE PRESENT RWY 24C HOLDING LINE ON TXWY Z SHOULD BE EBOUND HOLDING LINE FOR RWY 24L. THE GAP BTWN THE 2 HOLDINGS LINES SHOULD BE A SAFE AREA FOR ACFT TO SIT; NOT A FORBIDDEN AREA.