Learjet 31
Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP); Flight Crew Flight Instructor; Flight Crew Instrument
Flight Crew Last 90 Days 75; Flight Crew Total 3000; Flight Crew Type 1600
Confusion; Troubleshooting
Aircraft Equipment Problem Critical
Flight Crew Diverted
Aircraft
Climbing through FL430; I noticed the cabin altitude was unusually high; approximately 8;500 feet; with a different pressure of ~7.5 PSI. Suddenly; a large amount of air was forced into the cabin; lowering the inside cabin altitude by approximately 6;000 feet/minute. This was immediately followed by an increase in temperature. We suspected the emergency valves opened; and advised ATC to start us down lower. We ran the checklist for inadvertent activation of emergency airflow (I believe); then noticed fumes in the cockpit. It was then we decided to divert ASAP to ZZZ. No report of an emergency was ever made to ATC.
Lear-31 Captain reported unusually high cabin altitude; sudden air inflow; and fumes; possibly due to inadvertent activation of emergency airflow.