G550 Captain reported a Crew Alert System notification indicated BAGGAGE COMPT LOW PRESSURE in cruise. The flight crew descended to a lower altitude and followed the checklists and QRH. After consulting with maintenance personnel and the aircraft manufacturer; it was determined that the problem was most likely a faulty valve and the flight continued to destination airport.

Narrative

Enroute from ZZZZ - ZZZ; we were cruising westbound at FL430 just past ZZZ1 when a blue CAS (Crew Alert System) message popped up that said BAGGAGE COMPT LOW PRESSURE. We consulted the QRH checklist and it states that; 'Low pressure is detected in the baggage compartment.' The one corrective action says; 'Internal baggage door shall remain closed for the remainder of the flight.' Shortly after finishing reading this checklist; our Flight Attendant came forward and said there was an alarm going off in the back of the airplane. I asked the SIC (second in command); PM (pilot monitoring); to double-check his O2 mask to make sure it was securely in place and functioning correctly. I left my seat to go and investigate the 'alarm' that our Flight Attendant had mentioned.As I moved to the rear of the passenger cabin; I could hear a loud squealing noise; almost like the air being let out of a balloon when you hold the opening flat to restrict the exiting airflow. This noise was loudest in the aft lavatory near the interior baggage compartment door. I started to think there could be a leak around the exterior baggage door seal that had caused the baggage compartment to have low pressure and the air from the cabin was leaking into the baggage compartment. I advised the Flight Attendant and all of the passengers to not touch the baggage compartment door and I returned to the cockpit. After discussing the situation with the other pilot; we decided to descend to FL400. This would give us a slightly lower differential and a bit more time to react if the cabin pressurization started to leak. All of our pressurization instrumentation and systems synoptic pages were showing normal conditions in the cabin.I donned my O2 mask and the other pilot went back to listen to the noise in the cabin so he could make his own judgement about the situation. After he returned to the cockpit; we ran numbers and determined that FL340 is the lowest we could descend and still land at our destination with proper reserve fuel. We requested and received a descent to FL340. Our satellite phone was not working and our international internet was too slow over the water to make a phone call. I began texting with our maintenance personnel and they got on the phone with Gulfstream. After discussing the situation; they determined it was most likely a faulty valve that regulates the air between the baggage compartment and the cabin; and not the external baggage door seal. With this as the most probable cause of the problem and all of our pressurization systems showing normal; we continued the flight to our destination and landed uneventfully. A side note; the noise in the cabin was fairly loud at FL430. It was loud enough to hear halfway down the passenger cabin. After our descent to FL340; the noise was much quieter and could barely be heard in the passenger cabin with the lavatory door closed. After landing; our maintenance personnel checked the external baggage door seal and determined it was functioning properly and was not the cause of the baggage compartment low pressure event. They changed the suspected valve and all has functioned properly on the airplane during subsequent flights.