How helium and hydrogen methods work, what the equipment does, and how to pick a system for industrial or infrastructure leak testing.
A part that holds pressure on the bench can still leak in the field. Tracer gas testing exists for that gap. Instead of waiting for a gauge to notice a pressure drop, you fill the part with a gas that’s easy to detect and go looking for where it escapes.
This overview explains how helium and hydrogen tracer gas methods work, what the main pieces of equipment do, and how to choose a system for industrial or infrastructure leak testing. It also covers why calibrated, traceable instrumentation matters when the leak rates are tiny, and where a specialist supplier such as Applied Measurement Australia fits in.
Key Takeaways Helium mass spectrometry is the most sensitive method. Hydrogen, used as a 5% mix in nitrogen, is cheaper and easier to source, and suits many production and field jobs. A tracer gas system is more than a detector. Injection, probes, reference leaks, fixtures and data handling all shape the result. Choose from the leak-rate limit you need to prove, the part, the cycle time and the site, not from the gas alone. When accuracy matters, a leak result is only as trustworthy as the calibrated references and pressure instruments behind it.
Key Takeaways
Tracer gas leak detection fills a part, pipe or system with a gas that’s easy to detect, then measures where and how fast that gas escapes. It finds leaks that are too small for a bubble test and too subtle for a pressure gauge, and it can tell you where they are.
Leak rates are usually quoted in mbar·L/s, where 1 mbar·L/s equals 0.1 Pa·m³/s. Many production lines use pressure decay for the pass or fail decision, and ATEQ’s pressure decay range covers a lot of that ground. Tracer gas earns its place when the limit is tighter, when the part is large or awkward, or when you need to know where the leak is rather than only that it exists. Air Products lists utilities, telecommunications, transport and industry among the users of hydrogen leak detection gas.
A helium leak detector is a tuned mass spectrometer. It ionises the gas it draws in, separates the ions by mass, and measures how much helium is present. That makes it extremely selective and very sensitive.
There are two everyday ways to use it. In vacuum mode, the part is evacuated and connected to the detector, and helium is sprayed on the outside. Any helium that gets drawn in shows up as a signal, and the peak tells you where the leak is. In sniffer mode, the part is pressurised with helium and a probe is moved around the outside to sample the air.
Sensitivity differs a lot between the two. One published specification for a Leybold detector lists vacuum mode at 5 × 10⁻¹² mbar·L/s or better and sniffer mode at 1 × 10⁻⁹ mbar·L/s. Helium suits the job because it’s inert and non-toxic, occurs at only about 5 ppm in air, and is one of the smallest atoms, according to Leybold. The drawbacks, as Cincinnati Test Systems notes, are cost, supply and the fact that helium can permeate some materials, which can affect readings.
Hydrogen methods use a sensor instead of a mass spectrometer. The part is filled with forming gas, a mix of 5% hydrogen and 95% nitrogen, and a probe fitted with a hydrogen-sensitive sensor picks up any gas that escapes. The instrument sounds or lights up as the probe nears a leak.
The mix is safe to handle because ISO 10156 classes hydrogen and nitrogen blends below 5.7% hydrogen as non-flammable. Never use pure hydrogen for this work. Hydrogen also makes a good tracer physically. It’s the lightest gas, so it spreads through a part quickly and clears away fast, and the background level in air is only about 0.5 ppm, roughly a tenth of helium’s, as Leybold explains.
The trade-off is sensitivity. Hydrogen sniffers aren’t as sensitive as a helium mass spectrometer, so they won’t find the smallest leaks. In return, Assembly magazine notes that the equipment is substantially less expensive and needs no vacuum system.
The ATEQ H6000 is a good example of this class. Applied Measurement lists it as a compact hydrogen tracer gas detector with 128 programs, IP54 protection, 2 GB of internal memory, red and green LEDs with an audible alarm, a USB port and a battery good for about 8 hours. The listing gives a detection range of 1 × 10⁻⁴ to 2 × 10⁻² mbar·L/s and notes that hydrogen costs less than helium.
The detector gets the attention, but the result depends on the whole chain. Here’s what each part does and what to check when you compare systems.
If a supplier quotes only the detector, ask what’s missing. A sensitive instrument connected to a leaky fixture or an unregulated gas supply won’t give repeatable results.
Choose helium when you must prove very low leak rates or work on high-vacuum systems. Choose hydrogen when moderate limits, gas cost, availability or fast, portable testing matter more. Many production limits can be met with hydrogen, but check the numbers against your own specification.
The method decides how sensitive the test can be and how long it takes, so pick it alongside the gas.
Work backwards from what you need to prove. These steps keep the decision grounded:
For automotive components, sealed housings and packaging, the wider ATEQ leak testing range and the automotive testing applications page show how these choices play out in practice.
Hydrogen is the usual choice for buried pipes and other infrastructure because it’s cheap, safe in the 5% mix, and rises through soil to the surface. The technique suits small leaks, non-metallic pipes and short runs such as service pipes, as INFICON describes for water networks.
In outline, the operator isolates and empties the section, injects the tracer gas at low pressure (INFICON gives 0.5 to 1 bar for water pipes), then walks the route with a surface probe. A rise in hydrogen at the surface marks the leak. How long the gas takes to appear varies with soil, surface and pipe depth, so expect to wait.
Two cautions apply. First, follow your utility’s procedures and any regulations for the asset, particularly on gas networks. Second, check that the detector and probe are designed for surface scanning. A handheld sniffer built for production parts may not be the right tool for a street survey, so ask your supplier before you buy.
Leak rates are tiny numbers, so small errors can flip a pass into a fail. A result is only as reliable as the references behind it: the calibrated leak used to check the detector, the pressure and timing instruments, and the tracer gas mix.
Many test instruments build this in. ATEQ’s F570 series, for example, is calibrated from the front panel using a calibrated leak. That only helps if the calibrated leak itself has a certificate you can trust, and if you check the detector against it on a routine schedule. In automotive, aerospace and medical work, auditors will ask to see exactly that.
This is where a specialist supplier helps. Applied Measurement says its ATEQ range is backed by local stock, technical support and calibration. Its lab also calibrates pressure sensors and transmitters in-house against traceable reference standards, and you can pair test equipment with pressure transducers and data acquisition when you need to log more than pass or fail.
One point of accuracy. Applied Measurement’s NATA-accredited laboratory covers tension and compression force calibration up to 22 kN, so leak detectors and calibrated leaks aren’t part of that scope. Ask the team what calibration documents come with the equipment you’re buying and how they link to a reference standard. Our calibration services page sets out what the lab covers, and our guide on how to choose a calibration laboratory explains what to look for on a certificate.
Practical Tip Check the detector against a reference leak at the start of each shift, and log the reading. If the response moves, you find out before you’ve tested a batch rather than after it.
Practical Tip
Check the detector against a reference leak at the start of each shift, and log the reading. If the response moves, you find out before you’ve tested a batch rather than after it.
Applied Measurement Australia has supplied measurement and test instrumentation since 1976. Its ATEQ leak testing range covers pressure decay leak testers, tracer gas detectors, combined testers and valve testers, and its ATEQ leak testing overview explains how the range fits together.
In practice that means:
If you need a helium mass spectrometer system rather than a hydrogen sniffer, ask the team what’s available before you commit.
Sourcing Tip Before you request a quote, note the part or pipe, the leak-rate limit, your preferred tracer gas, the cycle time, whether testing is manual or automated, and what records you need. With that, the team can point you to the right method and confirm what calibration paperwork is available.
Sourcing Tip
Before you request a quote, note the part or pipe, the leak-rate limit, your preferred tracer gas, the cycle time, whether testing is manual or automated, and what records you need. With that, the team can point you to the right method and confirm what calibration paperwork is available.
In the standard 5% hydrogen, 95% nitrogen mix, yes. ISO 10156 classes blends below 5.7% hydrogen as non-flammable. Never use pure hydrogen for leak testing, and follow your site’s procedures and the gas supplier’s safety data sheet.
Helium with a mass spectrometer is more sensitive, especially in vacuum mode. Hydrogen sensors are less sensitive but cost less to run and need no vacuum system, which suits many production and field jobs.
The most common unit is mbar·L/s. You’ll also see Pa·m³/s and sccm. One mbar·L/s equals 0.1 Pa·m³/s. Always check which unit a specification uses before comparing instruments.
Yes. Hydrogen injected into an isolated pipe rises through the soil, and a surface probe detects it above the leak. It works well for small leaks and non-metallic pipes. Follow the asset owner’s procedures and confirm your detector suits surface scanning.
If accuracy matters, yes. A calibrated leak gives you a known value to check the detector against. Keep its certificate, check the detector on a routine schedule, and record the results so your test data stands up in an audit.
If you’re comparing tracer gas methods, start with the ATEQ leak testing range and the H6000 detector. When you’re ready to talk through your part, leak-rate limit and records, contact the Applied Measurement team for advice and a quote, or read more about us and our blog.
Contact Applied Measurement Phone: (03) 9874 5777 Email: sales@appliedmeasurement.com.au Location: 24a/49 Corporate Blvd, Bayswater VIC 3153 Hours: Monday to Thursday 09:00 to 17:00, Friday 09:00 to 16:00
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