A leak test that monitors pressure changes over time in an evacuated chamber containing the package.
Also called: vacuum decay leak test; pressure rise; vacuum decay.
What decays in a vacuum-decay leak test?
Chamber pressure is monitored after evacuation. Gas escaping from a leaking package can increase pressure in the evacuated chamber. The package is the test object; absolute or differential chamber pressure is the measured signal.
Keep the signal name explicit when comparing equipment. A load cell pressing against expanding lidding measures a different quantity, even when both systems use an external vacuum. A foil-deflection measurement is another approach again; “vacuum based” alone does not identify the sensor or analysis.
Can a very large leak look like a small stable signal?
A gross leak can prevent the system from reaching its required vacuum, while a smaller leak may be assessed through later pressure behaviour. Identify those assessments separately; not every leak appears as the same late-cycle pressure rise.
Use evidence for the actual package, headspace, fixture and cycle conditions, including relevant gross and small defects. A quoted micron capability without its challenge geometry and configuration is not a transferable limit for every blister cavity.