What was found
IN FLIGHT AROUND 10,000 FEET WE FELT AND SAW THE CABIN ALTITUDE RISING. IT CLIMBED TO 9650 AND WE GOT THE CAUTION AND WARNING MESSAGES. WE LEVELED OFF, RAN THE QRH AND RETURNED TO THE FIELD. RECEIVED ARES DOWNLOAD FROM TEAM 680 TEXTRON VIA EMAIL, WHICH ADVISED CHECKING THE VENT DOOR SWITCH (S4) AND INSPECTING THE CABIN DOOR HANDLE FOR SECURITY. PERFORMED PROXIMITY SWITCH TEST AND ADJUSTMENT AS OUTLINED IN AMM 52-70·10. ADJUSTED THE SWITCH TO A GAP OF0.10 INCH. CABIN DOOR HANDLE. INSPECTED DOOR COMPONENTS FOR ABNORMALITIES. NO ABNORMALITIES WERE FOUND. CONDUCTED AN OPERATIONAL CHECK OF THE CABIN DOOR, WHICH WAS SATISFACTORY AS PER AMM 52-10·00.