As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DUDRING TAKEOFF FROM BINGHAMTON REGIONAL AIRPORT, LEFT EMERGENCY PRESSURIZATION 3-WAY VALVE WENT TO EMERGENCY POSITION. PROBLEM INTRODUCED HOT AIR AND SMOKE INTO CABIN. VALVE WOULD NOT SHUT OFF. EMERGENCY DECLARED AND ACFT RETURNED AND AN UNEVENTFUL LANDING MADE. AIRCRAFT TURNED OVER TO MAINTENANCE. THE LT EMERGENCY PRESSURIZATION 3-WAY VALVE WAS REPLACED.