​​When it comes to leak testing, manufacturers have plenty of options—but two of the most widely used methods are vacuum chamber testing and accumulation testing. Choosing the right approach can mean the difference between accurate, reliable results and costly inefficiencies. At VES, we’ve spent decades perfecting both methods, helping manufacturers across industries select the right system for their specific needs.

So, what’s the difference between vacuum chamber and accumulation testing? And which one is best for your application? Let’s break it down.

How Vacuum Chamber Leak Testing Works

Vacuum chamber helium leak testing is one of the most precise methods available. The process works by placing the test part inside a sealed chamber and creating a vacuum. Helium is then introduced into the part (either directly or via a pressurised fill), and if there’s a leak, the helium escapes into the vacuum. A helium mass spectrometer detects even the smallest traces of the gas, providing an ultra-sensitive measurement of the leak rate.

Why Choose Vacuum Chamber Testing?

  • Extreme sensitivity – This method can detect leaks as small as 1 × 10⁻⁷ mbar∙L/sec, making it ideal for high-precision industries like aerospace, medical devices, and hydrogen fuel cells.
  • Reliable and repeatable results – Because the test environment is tightly controlled, vacuum chamber testing offers consistent, highly repeatable results, eliminating variability caused by external factors.
  • Comprehensive testing – Unlike spot-checking methods, vacuum chambers provide a full 360-degree test, identifying leaks anywhere on the part.

However, vacuum chamber testing isn’t always the right fit. The equipment is typically more complex and expensive, requiring a sealed chamber and a vacuum pump system. It’s also not ideal for large components, as the chamber size limits the parts that can be tested.

How Accumulation Testing Works

Accumulation testing is a simpler and more cost-effective method. Instead of using a vacuum chamber, the part is placed inside a sealed enclosure at atmospheric pressure. Helium is introduced into the part, and any escaping gas slowly builds up (or “accumulates”) in the enclosure. After a set period, a helium sensor measures the concentration of helium in the air inside the enclosure, determining whether the part passes or fails.

Why Choose Accumulation Testing?

  • Lower cost, smaller footprint – Since there’s no need for a vacuum pump or chamber, accumulation testing systems tend to be less expensive and require less floor space.
  • Better for larger parts – If your product is too large to fit inside a vacuum chamber, accumulation testing provides a practical alternative while still delivering reliable results.
  • Easier to integrate – Accumulation systems can often be added to existing production lines with minimal disruption.

That said, accumulation testing isn’t as sensitive as vacuum chamber testing. While it can detect leaks as small as 1 × 10⁻³ mbar∙L/sec, it’s not suitable for applications requiring extremely tight leak specifications. The cycle time can also be longer, as the helium must accumulate to a measurable level.

Which Leak Testing Method is Right for You?

Choose Vacuum Chamber Testing If:

  • You need the highest level of precision (down to 1 × 10⁻⁷ mbar∙L/sec).
  • Your components are small to medium-sized and can fit inside a vacuum chamber.
  • You require high repeatability and reliability in your test process.
  • Your industry demands stringent quality control, such as aerospace, medical devices, or hydrogen fuel cells.

Choose Accumulation Testing If:

  • Your parts are too large for a vacuum chamber (such as automotive fuel tanks or HVAC components).
  • You need a cost-effective leak testing solution.
  • Your leak rate requirements are above 1 × 10⁻³ mbar∙L/sec.
  • You want an easier integration into your existing production line.

In many cases, a combination of both methods may be the best solution. For example, a manufacturer might use accumulation testing for a general quality check and vacuum chamber testing for critical components that require the highest precision.

Finding the Right Leak Testing Solution for Your Needs

At VES, we understand that every application is unique, and choosing the right leak testing method is essential for maintaining product integrity, safety, and efficiency. Whether you need the extreme sensitivity of vacuum chamber testing or the flexibility of accumulation testing, we can help you design a solution that meets your exact requirements. If you’re unsure which method is best for your operation, reach out to our team—we’d be happy to guide you through the process.