INFICON :: LEAK TEST - Best Practices for Leak Detection

Helium vs. Hydrogen

Which gas is best for your application?

In the previous issue of LEAK TEST newsletter, we announced that INFICON added the Sensistor product line to its portfolio. In this issue, you'll learn which leak detection products are best-suited for your application.

Sniffing Applications

Sniffer leak detection gives you the benefit of not only discovering a leak, but also where the leak is (e.g., for repair later on). INFICON offers two designated sniffer leak detectors: the Protec P3000(XL) and the Sensistor ISH2000. The Protec P3000(XL) requires helium as the tracer gas, while the Sensistor ISH2000 uses a mix of 5% hydrogen in 95% nitrogen (often called forming gas).

INFICON offers you the best of both worlds with two products and gases that cover all your needs for finding and quantifying leaks within your products.

The Sensistor leak detectors and forming gas excel in helping you identify leaks of a size that would leak liquids such as water, fuel or oils.

The Protec P3000(XL) and helium are the best choice if you need to find leaks that would leak minute quantities of gas, such as refrigerant leaks. Other factors may also influence your choice, such as ratio of small vs. large leaks and gas consumption, as forming gas is usually less expensive than helium.

Sensistor ISH2000 vs. Protec P3000(XL)

Accumulation Testing

Sometimes you may only require a good-part/ bad-part test by testing the entire product for leaks. This is usually done by placing the part to test in a chamber where it is pressurized with tracer gas. The gas that escapes through leaks in the test part is accumulated in this chamber, and analyzed by a gas detector. Accumulation testing can be a very effective way to integrally check objects for leaks without the need for a large and expensive vacuum chamber system. INFICON offers two products for this application: The T-Guard Helium Sensor and the Sensistor ISH2000 in combination with the AP29 sampling probe. T-Guard uses helium as the tracer gas whereas the Sensistor accumulation system employs forming gas (5% hydrogen in 95% nitrogen) as the tracer gas. Note: Helium is usually slightly more expensive than forming gas.

The graphic below shows the optimal choice of either accumulation system during a 20 second accumulation time. For any combination of leak rate and free volume of the accumulation chamber (volume of accumulation chamber minus volume of part under test), the Sensistor ISH2000 with AP20 sampling probe should be the favored solution due to gas cost. For more demanding applications (i.e., lower leak rates for given volume or larger free volume of the accumulation chamber), the T-Guard system is the better choice.

Accumulation time = 20 s

If you can allow for more accumulation time, the triangle which indicates the usable range for the Sensistor ISH2000 with AP29 sampling probe is extended to the top of the graphic ( i.e., there is a trade-off between saving on gas cost and achievable throughput).

Accumulation time = 60 s

For more information on choosing the best gas for your application, contact your local INFICON support center. You can also email us at, or click here to request someone contact you.


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Spring 2012
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Helium vs. Hydrogen
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