FILL
Charge the part with helium or hydrogen forming gas to the programmed test pressure.
Helium Leak Test Method
Sniffing Leak Test
Sniffing leak testing charges a part with trace gas and scans its seams with a probe, producing a signal peak at the physical leak site.
Sniffing, or sniffer leak detection, is a trace-gas method for finding where a part leaks. The part is charged with helium or 5%/95% hydrogen forming gas, then a probe follows welds, joints, seals and fittings.
The probe continuously samples the surrounding air. Over a leak, escaping trace gas enters the probe and creates a signal peak that identifies the site and indicates its approximate leak rate.
Sniffing routinely finds leaks in the 10⁻⁵ to 10⁻⁷ mbar·l/s range without a vacuum chamber or immersion. It complements whole-part methods that measure total leakage.
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How is Leak Rate Calculated →What is a sniffing leak test?
Sniffing turns a trace-gas result into a physical location. The detector samples air close to likely leak features instead of measuring pressure change in the part.
An operator or programmed motion follows welds, joints, seals and fittings. Background stays low away from a leak and rises locally where charged gas escapes.
This method needs neither a vacuum chamber nor immersion. It provides direct investigation of a rejected assembly and an approximate leak-rate indication at the site, typically in the 10⁻⁵ to 10⁻⁷ mbar·l/s range.
The probe turns a leak result into a location. An operator or programmed motion follows likely leak features, including welds, joints, seals and fittings. Background stays low away from a leak and rises locally where trace gas escapes.
Sniffing uses neither a vacuum chamber nor immersion. After the part is charged with the selected trace gas, the detector samples air near suspected leak paths. This supports direct investigation of a rejected assembly and an approximate leak-rate indication at the site.
Recorded sniffing results can be used with whole-part testing: the whole-part method establishes total leak behavior, while the probe identifies the area for rework evaluation.
How a sniffing test runs
SCAN
Move the sniffer probe along welds, joints, seals and fittings.
DETECT
The probe samples surrounding air and the detector reports a signal where trace gas escapes.
VENT
Complete the scan and vent or recover the test gas under the programmed sequence.
A signal within the programmed reject limit passes; a signal above the limit identifies a leak location for evaluation.
When sniffing is the right method — and when it is not
Sniffing is a fit when
- ✓A need to pinpoint the physical leak site
- ✓A part that can be charged with helium or forming gas
- ✓Rework decisions after a whole-part leak result
Choose another method when
- →A need for the most sensitive total leak rate — Use hard vacuum leak testing.
- →A finished hermetic part with no fill port — Use bombing leak testing.
- →A total result for a large part in a hood — Use accumulation leak testing.
Sensitivity, cycle time and part volume
Sniffing measures trace gas at the probe rather than pressure change in the part. A signal peak occurs when the probe passes over escaping gas.
The scan path covers welds, joints, seals and fittings, and detector response identifies the local area for rework or investigation.
Helium and forming gas are trace-gas options. The sequence prepares and charges the part before scanning, then records the detector result.
A consistent scan path makes results more comparable from part to part.
The detector samples air close to suspected leak paths after the part is charged with the selected trace gas.
A whole-part test can establish total leakage while sniffing identifies the area for rework evaluation.
The scan can follow the same defined features on every part, giving operators a consistent trace-gas path.
The recorded scan supports a clear follow-up decision for the assembly.
Which Zaxis testers run sniffing
Sniffing needs a helium-charged part and a probe-fed detector. Z-Charge charges the part; Z-Ion reads the probe signal and flags the leak site.
Z-Charge + Z-IonA coordinated controller and helium mass-spectrometer detector for helium test sequences.
Z8An 8-inch modular platform for programmed leak-test sequences and recorded results.Applications for sniffing testing
HVAC/R assemblies
Charged assemblies can be scanned at joints and fittings to locate a leak.
EV battery systems
Sealed battery-related components can be scanned where a physical leak location is needed.
Medical devices
Charged medical components can be scanned along seals and joints for rework evaluation.
Sniffing vs other leak test methods
| Method | Non-destructive | Needs an access port | Locates the leak | Typical use |
|---|---|---|---|---|
| Pressure decay | ✓ | ✓ | × | Sealed parts with a port |
| Vacuum decay | ✓ | ✓ | × | Parts and packaging |
| Mass flow | ✓ | ✓ | × | Flow-rate limits |
| Occlusion | ✓ | ✓ | × | Blocked passages |
| Burst | × | ✓ | × | Failure pressure |
| Pressure cracking | ✓ | ✓ | × | Valve opening pressure |
| Chamber | ✓ | × | × | Sealed parts, no port |
| Sniffing | ✓ | ✓ | ✓ | Finding the leak site |
| Hard vacuum | ✓ | ✓ | × | Hermetic, safety-critical parts |
| Accumulation | ✓ | ✓ | × | Large parts, total leak rate |
| Bombing | ✓ | × | × | Sealed parts, no fill port |
| Differential pressure | ✓ | ✓ | × | Large volumes, low leak rates |
| Trace gas | ✓ | ✓ | ✓ | Very small leaks, quantified |
Sniffing leak test FAQ
What is sniffing leak testing?
It charges a part with trace gas and scans welds, joints, seals and fittings with a probe that samples surrounding air.
What does a sniffer probe detect?
It detects escaping helium or hydrogen forming gas and produces a signal peak at the leak site.
Can sniffing locate a leak?
Yes. It is the trace-gas method used to pinpoint the physical leak site.
How sensitive is sniffing?
It routinely finds leaks in the 10⁻⁵ to 10⁻⁷ mbar·l/s range.
Does sniffing need a vacuum chamber?
No. It is performed without a vacuum chamber or immersion.
What gases can be used?
Helium or 5%/95% hydrogen forming gas can charge the part before scanning.
How does sniffing complement hard vacuum?
Hard vacuum measures a whole-part total leak rate, while sniffing identifies where a leak is located.
Related leak test methods
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