Leak / Vacuum Tester
Checks that packs and containers are sealed, by pulling a vacuum around them and looking for dye ingress, bubbles or a rise in chamber pressure. Covers simple blister leak tests and deterministic vacuum-decay CCI testing.
- Pharmaceutical
- Medical devices
- Food packaging
- Nutraceutical
What is Leak tester?
A leak tester puts a sealed pack in a chamber and lowers the pressure around it. If the pack has a leak, the pressure difference drives air out of the pack, or drives liquid (often coloured dye) into it when the vacuum is released.
The simplest form, common in tablet and capsule packing areas, is a vacuum desiccator-style chamber filled with methylene blue solution. Blister strips are held under the dye at a set vacuum for a set time; after release, any pocket with blue dye inside has failed. This is a probabilistic test because the result depends on chance and on the analyst seeing the dye.
For sterile products, container closure integrity (CCI) is tested with deterministic methods such as vacuum decay. The tester evacuates a close-fitting chamber around a vial or syringe, isolates it and measures the pressure rise with a sensitive transducer. A leak lets gas or vapour escape into the chamber and the pressure rises more than the validated limit. USP <1207> prefers deterministic methods because they measure a physical quantity and are less subjective.
Used for
- Blister and strip pack leak test (methylene blue dye, in-process and release)
- Container closure integrity of vials, ampoules, prefilled syringes and bottles
- Seal integrity of sachets and pouches
- Stability CCI testing in place of sterility testing at later time points (where justified)
- Packaging development and change control
How it works
- 01
Load
The pack or container is placed in the test chamber (submerged in dye for a dye test).
- 02
Evacuate
A vacuum pump reduces the chamber pressure to the set level.
- 03
Hold / isolate
The vacuum is held for a set time; in vacuum decay the chamber is isolated from the pump.
- 04
Measure
Pressure rise is measured (vacuum decay) or bubbles are watched (bubble test).
- 05
Release
The vacuum is released; for dye tests the atmospheric pressure pushes dye into any leak.
- 06
Judge
Packs are inspected for dye, or the pressure result is compared with the pass/fail limit.
Advantages
- Dye and bubble tests are simple and cheap
- Vacuum decay is non-destructive, quantitative and sensitive
- Vacuum decay results are objective and data can be stored electronically
- Leak tests detect seal faults before products reach patients
Limitations
- Dye ingress is destructive and depends on the analyst's eyesight
- Probabilistic tests can miss small leaks
- Vacuum decay needs product-specific test parameters and validation with positive controls
- Very small leaks may still need more sensitive methods (e.g. helium leak, high-voltage leak detection)
Methods that use Leak tester
Keep every Leak tester in control: usage logs, calibration and maintenance schedules, and automatic blocking of overdue instruments.