Jet liners do not need to descend to feed ambient air into the plane. Cabin pressurization is done by feeding compressed air from the engine to air conditioner

Jet liners do not need to descend to feed ambient air into the plane. Cabin pressurization is done by feeding compressed air from the engine to air conditioner and then to cabin. So in theory yes, this is possible. However in case of fire, actively feeding fresh air may make things worse by providing more oxygen to burn.