How to choose a helium leak detector
A helium mass-spectrometer leak detector pumps the part under test, then tunes a small magnetic-sector analyser to mass 4. Helium is used because it is small, inert, safe and rare in air, so any signal above background is a leak. Detectors reach the 10⁻¹² mbar·L/s decade — far beyond what pressure decay or bubble testing can resolve.
The first decision is test mode. Vacuum (outside-in) mode sprays helium on an evacuated part and gives the lowest detectable leak rate; sniffer (inside-out) mode pressurises the part and probes the outside, which is faster for large assemblies and locates leaks precisely. Then look at minimum detectable leak rate in each mode, start-up time to test-ready, maximum inlet pressure and test-port size, whether the backing pump is dry or oil-sealed, and how calibration is handled — an internal calibrated leak makes daily verification a one-button job.
Typical duties: HVAC and refrigeration manufacturing, automotive fuel and battery systems, semiconductor and vacuum equipment build, aerospace, medical devices, and vacuum-system commissioning. Consumables — filaments, ion source parts, calibrated leaks and sniffer probes — decide uptime, so plan them with the instrument.
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FAQ
What is the smallest leak a helium mass spectrometer can detect?
In vacuum mode a well-maintained instrument resolves down to the 1x10⁻¹² Pa·m³/s range; in sniffer mode the practical limit is several orders coarser because the probe samples ambient air. The specification only holds after calibration against a known leak standard and with a clean, dry test object.
Vacuum mode or sniffer mode — which do I need?
Vacuum mode when the part can be evacuated and you need the total leak rate with the best sensitivity. Sniffer mode when the part is pressurised with helium and you need to locate the leak, or when the part cannot be pumped down. Many production lines use both: vacuum mode to accept or reject, sniffer to find the spot.
How often should the leak detector be calibrated?
Calibrate against an internal or external standard leak at least at the start of every shift, and again after any filament change, ion source cleaning or transport. Quality systems generally also require an annual calibration of the standard leak itself, because its emission rate drifts with time and temperature.
Do you supply spare parts for Pfeiffer/Adixen ASM and Leybold/INFICON detectors?
Yes — ion source filaments, electron multipliers, analyser cell parts, calibrated leaks, sniffer probes and filters, valve bodies and solenoid valves for the common ASM, ASI, Modul and UL families. Send the instrument model and the part number; compatible parts are labelled as compatible and genuine parts are labelled as genuine.
Why does the background signal stay high after pumping down?
Usually helium already dissolved in elastomer seals or trapped in the test object from a previous test, an internal leak in the instrument's own valve block, or a saturated ion source after a large helium spill. Let the system pump overnight, retest a known-good part, and if the background still will not fall, the valve block or the ion source needs service.