Will the Z1/Z2 work at an elevation above 8,000 ft.?

Our units have been tested for up to 8,000 feet. We cannot guarantee the operation of the device above 8,000 feet. Note: The Z1/Z2 will work in an aircraft flying higher than 8,000 feet because the cabin is pressurized to 11 to 12 psi, approximately the atmospheric pressure at 6,000-8,000 feet.