CL604 CAPT MADE AN EMER DESCENT DUE TO CABIN ALT WARNING AND ADJUSTING PRESS VIA MANUAL HAD NO AFFECT. HOWEVER; AFTER DESCENDING TO AN ACCEPTABLE ALT; THE CAPT REMEMBERED HE HAD SHUT OFF BOTH ENGINE PACKS ON THE GND DUE TO EXHAUST INGESTION; BUT HAD NOT TURNED THEM BACK ON.

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TURNED PACKS OFF ON GND DUE TO EXHAUST INGESTION. FORGOT TO TURN ON PRIOR TO TKOF. CLIMB CHK PERFORMED BY ME (CAPT PNF) APPEARED NORMAL. AT FL230 OR SO THE CABIN ALT CAUTION OCCURRED AND WE REQUESTED DESCENT AND DONNED MASKS PREMATURELY ANTICIPATING EMER SIT. CABIN ALT WARNING OCCURRED AND WE PERFORMED MEMORY CHKLIST AND BEGAN MORE RAPID DESCENT; DEPLOYED PAX O2. I RETRIEVED EMER CHK AND ATTEMPTED A MANUAL CTL OF PRESSURIZATION. AT THAT POINT I REALIZED THE PACKS WERE OFF. I TURNED PACKS ON AND ACFT REGAINED NORMAL CTL. WHAT I FEEL I DID WRONG OTHER THAN THE OBVIOUS FORGETTING PACKS ON: COULD HAVE RECOGNIZED AN ABNORMAL (YET STILL INDICATING GREEN) CABIN ALT DURING CLIMB CHK. COULD HAVE CHECKED PACKS ON DURING CLIMB CHK CALL OF 'PRESSURIZATION ON CHK.' COULD HAVE INITIATED THE ABNORMAL CABIN ALT CHECK AS SOON AS IT OCCURRED (WHICH INCORPORATES A CHK OF PACKS) RATHER THAN BEGIN IN DESCENT AND BEGIN PREPARING FOR THE EMER WHICH HAD NOT YET OCCURRED. EMER CHK DOES NOT CONSIDER TROUBLESHOOTING; ONLY ESCAPING A POTENTIALLY DANGEROUS SIT.