What was found
FLT#915, JFK-SFO. 'PASSING THROUGH 9,000 FEET IN THE DESCENT WE COULD SMELL A MUSTY DIRTY SOCKS SMELL. VERY NOTICEABLE IN THE FLIGHT DECK. TURNING PACK 1 OFF STOPPED THE SMELL. BOTH PILOTS HAVE MILD HEADACHES AND NOSE IRRITATION, WHICH DEFINES THIS AS A LEVEL 2 EVENT AS PER FOM AND INFO NOTICE; INFO NOTICE 2017-T015 COMPLIED WITH. IAW BOTH NFO NOTICE PREVIOUS, AND TSM 05-50-00-810-831-A, INCIDENT IDENTIFIED AS A LEVEL "B". PERFORMED DECONTAMINATION PER AMM 21-00-00-615-803-A & 36-10-00-615-801-A . NO ODOR NOTED AND A / C ACCEPTABLE FOR CONTINUED REVENUE SERVICE.'