What was found
(CAN) APPROXIMATELY 10 MINUTES AFTER DEPARTURE THE CREW NOTED AN ABNORMAL SMELL IN THE COCKPIT. THE RECIRC FANS WERE SUSPECT & WERE SELECTED TO OFF IAW THE CHECKLIST. THE SMELL DISSIPATED & THE FLIGHT CONTINUED. WITHIN 10 TO 15 MINUTES THE SMELL RETURNED IN THE COCKPIT & THE CREW ELECTED TO DIVERT TO THE CLOSEST AIRPORT AS A PRECAUTIONARY MEASURE TO HAVE THE ACFT INSPECTED. PRIOR TO LANDING THE SMELL AGAIN DISSIPATED & THE ACFT LANDED WITHOUT INCIDENT. MX WAS DISPATCHED TO INSPECT THE ACFT FOR POSSIBLE CAUSES & DETERMINED THAT THE RT ACM FOR THE ENVIRONMENTAL SYS WAS AT FAULT. THE SYS WAS DISABLED IAW THE MEL & THE ACFT RETURNED TO BASE FOR ADDITIONAL MX. THE ACM IS HAS BEEN REPLACED & THE SYS INSPECTION COMPLETED WITH NO ADDITIONAL FAULTS.