If it leaks at all, helium finds it.

Because they measure leaks that differ by a factor of a thousand or more, and for the parts this system exists for, that gap is decisive. A pressure-decay test fills the part, isolates it and watches the pressure fall — simple, robust and perfect for a coarse leak, but its practical floor is around 10⁻³ to 10⁻⁴ mbar·L/s, and it gives a pass/fail without saying where the leak is. A helium mass-spectrometer works on completely different physics: it uses helium as a tracer gas — the smallest safe inert molecule, present in air at only about 5 ppm — and a mass spectrometer tuned to helium detects the tiny amount that comes through a leak, resolving down to about 10⁻¹² mbar·L/s and reporting a quantified rate, not just a verdict. For a vacuum chamber, a cryostat, a sealed sensor or a fuel element, the leak that matters is far below what pressure decay can even see, so helium mass-spec is the reference method. It is not that pressure decay is wrong — it is the right tool for a coarse spec — but when the specification is tight and the leak must be located and numbered, this is what the job needs.

They are three ways to bring helium and the detector together, chosen to fit the part. In the vacuum (outboard) test, the part is evacuated and connected to the detector, and helium is sprayed on the outside; any helium that leaks in is drawn straight to the mass spectrometer — this is the most sensitive mode, and it both quantifies the total leak and, by moving the spray, locates it. In the sniffer (inboard) test, the part is pressurised with helium and a probe is moved over the outside to find where helium escapes — less sensitive, but ideal for a large, open or already-installed assembly that cannot go into a vacuum chamber. The bombing / accumulation test is for hermetically sealed parts that have no port to connect to — sealed electronics, sensors, cans: they are placed in a bombing chamber and surrounded by high-pressure helium, which is forced through any leak into the sealed cavity, and then they are moved to a vacuum or accumulation chamber where the helium leaking back out is measured. Choosing the right method, and engineering the chamber, fixturing and sealing for it, is most of what makes a leak-test system work.

They are separate machines for separate jobs, which is why we build them as different products. Our helium charging and boosting / decanting stations handle helium — they fill, compress and transfer it — but they do not detect leaks; they are gas-handling systems. Our pressure-loss and high-pressure leak-test rigs use the pressure-decay method described above — coarse, robust, pass/fail — and our hydraulic-hose and CNG-circuit leak testers are pressure/bubble tests for those specific products. The dynamic high-pressure hydrogen leak rig uses hydrogen as the tracer for high-pressure hydrogen systems, a safety-driven niche. This system is the helium mass-spectrometer method: a different tracer, a different detector and a sensitivity orders of magnitude finer, giving a located, quantified micro-leak. So across the range we cover the whole spectrum — coarse pressure-decay and bubble testing at one end, and helium mass-spec at the other for the smallest, most critical leaks — and we will tell you plainly which one your specification actually calls for.

A leak rate is how much gas passes through a leak in a given time at a given pressure difference, quoted in mbar·L/s (millibar-litres per second) — it turns “it leaks” into a measured number you can hold against a specification. A part is not simply “leak-tight” in absolute terms; it is leak-tight to a rate — say better than 10⁻⁹ mbar·L/s — and that acceptance figure comes from the application (a vacuum vessel, a refrigerant circuit and a fuel element each have very different limits). To make the reading trustworthy, the detector is calibrated with a reference or standard leak: a small, precisely-known, temperature-corrected leak element that emits helium at a certified rate. Before and during testing, the instrument is set against that known leak, so the number it reports for your part is traceable and repeatable rather than an arbitrary meter reading. That calibration is what lets a leak test be an acceptance test — a documented, auditable number — instead of just an operator’s impression, and it is why the reference leak is part of the system, not an afterthought.

With the bombing test, which is designed for exactly that. A hermetically sealed device — a sealed sensor, a microelectronic package, a sealed source or can — has no valve or port to pressurise or evacuate through, so you cannot connect a detector to its inside. Instead you put it in a bombing chamber and surround it with helium at high pressure for a set time; if there is a leak, helium is slowly forced through it into the sealed internal cavity. The part is then removed and placed in a vacuum or accumulation chamber connected to the mass-spectrometer, where any helium now trapped inside slowly leaks back out and is measured. A large (gross) leak shows up quickly; a very fine leak takes longer to accumulate but is still caught. The timing of the bombing and the measurement, and the pressures used, are engineered to the part and the leak-rate limit so the test neither misses a real leak nor falsely flags a good part — and it is the standard way hermeticity is proven for sealed electronic and sensor components to military and space standards.

We integrate a bought-in detector into a complete, engineered test system — and we are clear about the split. The helium mass-spectrometer leak detector itself, the calibrated reference leak and the vacuum pumps are specialist precision instruments from established makers, chosen for the sensitivity and throughput your work needs. What Neometrix designs and delivers is everything that turns that detector into a working leak-test system for your part: the vacuum test chamber and the bombing and accumulation chambers, the part fixturing and sealing, the evacuation and the helium supply and recovery, and the automation, cycle control and traceable reporting — plus installation, commissioning and acceptance. It draws directly on the same vacuum-chamber and helium-handling competence behind our thermal-vacuum chamber and helium-charging systems, so the chamber-and-helium half of the job is very much our own engineering. To be plain about status: this capability is offered turnkey and quoted against helium leak detection requirements; no specific delivered system is claimed on this page.