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Leak Testing in Automotive, Aeronautics and Refrigeration

Leak testing ensures tightness in safety-critical systems. Among the many available methods, integral leak testing is one of the most common solutions for fast production cycles and stringent cost-efficiency.

Maximizing safety and performance with integral leak testing

Integral leak testing (accumulation or hard vacuum test) is not only about meeting standards – it is essential for ensuring product safety, quality and functionality by measuring the total leak rate of a test specimen or vessel under vacuum or positive pressure conditions.

While several leak detection methods exist, each suited to different technical and functional requirements, integral leak testing has emerged as one of the most widely used approaches in industrial applications.

Learn how to select the right leak detection method and understand how pressure differences impact results in our FAQ section.

By detecting unacceptable leak rates, integral leak testing ensures:

  • Product reliability: It guarantees that products function reliably across their lifecycle, mitigating potential failures.
  • Environmental compliance: The testing minimizes ecological impacts, aligning with environmental standards.
  • Industry conformity: It plays a crucial role in optimizing production and maintaining strict adherence to industry standards.

Leak detection technology from Pfeiffer – systems and components to detect leaks

From tracer gas and air leak detectors to high-performance vacuum pumps and accessories, Pfeiffer delivers reliable, efficient solutions tailored to your needs. Our offering includes:

  • Stand-alone leak detectors – ready for immediate use in manual or semi-automated testing environments, capable of detecting a wide range of leaks with helium, forming gas or hydrogen.
  • Integrable leak detectors – ideal for integration into existing production lines or custom systems and fast response times.
  • Turnkey leak test systems – fully automated, high-throughput setups that reliably detect leaks even in complex test scenarios.
  • Vacuum technology and components – including turbomolecular, rotary vane, and scroll vacuum pumps as well as vacuum boosters, vacuum chambers, gauges, valves, and more.

Learn more about choosing the right setup for your application in our FAQ section.

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Adapting leak testing to application-specific needs

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Integral leak testing in automotive industry

Modern vehicles consist of numerous systems – powertrain, safety, electronics – each requiring precise leak testing to ensure long-term reliability and compliance.

Traditional methods like bubble testing are still in use, but integral leak testing has become the preferred solution in the automotive industry thanks to its automation potential, high sensitivity, and reliability.

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Key challenges in the automotive industry

  • Very short cycle times
  • High system availability and throughput
  • Varying leak rate specifications per component
  • Need for reproducible, automated results

Why leak testing?

  • Long-term functionality of components throughout their lifetime
  • Product safety – ensuring proper functionality
  • Compliance with regulations

Typical components tested

Powertrain and chassis
Fuel system and battery
Cooling and safety
Final assembly
  • Engine block and head
  • Drive axles
  • Transmission
  • Shock absorber
  • Wheels
  • Electronic controls
  • Lights
  • Fuel tank and lines
  • Fuel vapor management system/components
  • Tank filler cap
  • Fuel pump and filters
  • Injection systems
  • (Lithium ion) battery
  • Fuel cell
  • Brake lines and fluid reservoir
  • Air-conditioning hoses and compressors
  • Air-conditioning condensers
  • Radiators and heat exchangers
  • Airbag ignitors and generators
  • Air-conditioning systems
  • Fuel system
  • Powertrain oil circuit
  • Powertrain water circuit
  • Engine water circuits
  • Cooling circuit e-battery

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Integral leak testing in aeronautics

In aerospace, failure is not an option. Every component – from control systems to landing gear – must be rigorously tested for integrity.

Integral leak testing ensures the structural soundness and airtightness of safety-critical systems across aircraft and space technologies.

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Key challenges in the aeronautics industry

  • High sensitivity for testing low leak rates
  • High repeatability and reproducibility of test results
  • Complex part geometries

Why leak testing?

  • Long-term functionality of components throughout their lifetime
  • Product integrity contributing to overall flight safety
  • Compliance with stringent aerospace standards

Typical components tested

  • Fuel systems
  • Hydraulic lines
  • Airframes
  • Components for space travel, turbines
  • Engine parts
  • Landing gear (shock absorbers, cylinders)
  • Braking (brake pistons, hoses)
  • Control systems

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Integral leak testing in HVAC-R industry

From residential heat pumps to industrial cooling systems, heating, ventilation, air conditioning, and refrigeration (HVAC-R) components must be leak-tight to ensure energy efficiency, safety, and environmental protection.

Unlike the sniffing method, integral leak testing quantifies total leakage.

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Key challenges in the HVAC-R industry

  • Environmental and regulatory pressures (e.g. F-Gas Regulation)
  • Large volume components
  • Short test cycles and high repeatability

Why leak testing?

  • Environmental compliance through product tightness
  • Regulatory compliance (e.g. F-Gas Regulation)
  • Long-term functionality and safety of parts

Typical components tested

  • Refrigerant lines (suction, discharge, liquid)
  • Refrigerators
  • Cooling systems, e.g. in hospitals, airports, offices, supermarkets
  • Air-conditioning, e.g. in cars
  • Heat exchangers
  • Condensers
  • Compressors
  • Evaporator coil
  • Valves
  • Filter driers
  • Receiver tanks
  • Accumulators
  • Hoses or tubing
  • Heat pumps
  • Radiators

Get your integral leak test solution!

Ensure product safety, functionality, and compliance with high-precision leak detection.

Our reliable and fast solutions ensure short cycle times, maximize throughput, and integrate seamlessly into automated production lines – customized and optimized for your individual process requirements.
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Customer success story

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Collaboration between Pfeiffer and Nolek

One of our most trusted collaborations in the field of integral leak testing is with Nolek, a global expert in leak testing and automation. Learn how Pfeiffer supplied crucial components – leak detectors, measurement equipment, and vacuum pumps – to Nolek, enhancing their HVAC-R leak detection capabilities.

This partnership highlights our dedication to providing precise and reliable solutions that support industry needs.

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Learn more about leak testing

What is integral leak testing and when is it appropriate?

Integral leak testing measures the total leak rate of a component or system to verify it meets functional tightness requirements. Unlike local leak testing, which pinpoints the leak location, integral testing focuses on overall performance and tightness under real-world conditions.

It is commonly used in:

  • Safety-critical applications like automotive, aerospace, and HVAC-R
  • High-throughput production environments
  • Systems where quantifying leakage is more important than locating it

Common methods include:

  • Pressure rise/pressure decay
  • Hard vacuum leak detection
  • Bombing tests

In helium-based vacuum tests, helium gas is used as a tracer because it is inert, small, and easy to detect. The gas is carried into or out of the test specimen depending on the differential pressure, and is measured using a mass spectrometer for ultra-sensitive results.

For more details on test methods and tracer gases (like helium or hydrogen), see our leak detection technology overview.

What is the difference between bubble testing and integral leak testing?

Bubble testing and integral leak testing are both non-destructive methods, but they differ significantly in precision, automation, and suitability for industrial applications.

Aspect
Bubble testing
Integral leak testing
Sensitivity
Low to medium
High
Detection method
Visual (manual inspection)
Automated measurement
Human error susceptibility
High
Low
Speed
Slow, time-intensive
Fast, suitable for automated lines
Material suitability
Limited (non-waterproof materials)
Broad (many material types)
Environmental influence
Medium (drying, corrosion risk)
Low
Standards compliance
Yes
Yes
Repeatability
Low (visual inspection variability)
High
Costs
Low to medium
Medium to high
Measurement type
Qualitative – visual (unless air is measured)
Quantitative – measures exact leak rate

Bubble testing may still be used for simple visual checks or prototypes, but integral leak testing is the method of choice in modern production for its reliability, automation potential, and quantifiable results.

How do I choose the right leak detection method?

Choosing the right leak detection method depends on several factors – from the purpose of the test to the component’s real-life operating conditions. The pressure inside the test specimen plays a crucial role in determining which method to use.

Key questions to ask:

  • Do I need to quantify the total leak rate or locate the exact leak?
  • What are the tightness requirements based on function and regulatory standards?
  • Is the unit pressurized or under vacuum during operation?
  • What cycle time, sensitivity, and test environment can my process tolerate?

No system is 100% tight. Leak testing should confirm the required functional tightness – preventing ingress or egress of fluids, gases, or contamination under real conditions.

Need help defining your leak rate or test setup? Talk to our experts or explore our leak testing services.

What is the difference between vacuum and overpressure leak testing?

Overpressure leak testing involves pressurizing a component with a gas (often air or nitrogen) to a level above atmospheric pressure. The component is then monitored for any loss of pressure or escape of gas, which would indicate a leak. This method is particularly suitable for components that are designed to operate under positive pressure, such as systems like pipelines, valves, and pressure vessels.

Vacuum leak testing, on the other hand, involves evacuating air from the component or system to create a vacuum environment. Leaks are detected by observing how quickly the vacuum degrades or by introducing a tracer gas (commonly helium) and using a helium mass spectrometer to detect any gas escaping into the vacuum chamber.

Vacuum testing offers higher sensitivity, often capable of detecting extremely small leaks (down to 10⁻⁹ mbar·l/s or lower), which makes it ideal for components designed to operate under vacuum or when ultra-sensitive leak detection is required.

Tracer gases like helium enhance both overpressure and vacuum testing by increasing detection sensitivity. In overpressure methods, helium can be used and detected by a sniffer probe. In vacuum methods, helium introduced outside the sealed component will be drawn in through leaks and detected by the spectrometer.

What is envelope leak testing?

Envelope testing is a specific form of integral leak testing. It involves placing the test object in a sealed chamber (the “envelope”) and introducing a tracer gas under vacuum or pressure. If there is a leak, the gas enters or escapes the object and is detected by a connected leak detector.

Benefits of envelope testing:

  • High sensitivity (e.g. for very small leaks)
  • For components with complex shapes or multiple potential leak paths
  • Testing under vacuum or pressure conditions simulates real-world use

What’s the right leak detection setup: stand-alone, integrable, or turnkey?

Leak detection setups are not one-size-fits-all. At Pfeiffer, we offer three scalable solutions – all built with our own vacuum technology and components:

  • Stand-alone leak detectors
    Ready-to-use for manual or semi-automated testing – ideal for laboratories, R&D, or flexible production lines.
  • Integrable leak detectors
    Designed for seamless integration into production lines. These detectors come with flexible interfaces and can be tailored to specific high throughput cycle times and leak rate requirements.
  • Turnkey leak test systems
    Fully automated, high-throughput solutions – complete with chambers, vacuum pumps, gauges, valves, and software – for customers seeking ready-to-run installations.

Not sure which approach fits your needs best? Explore our Leak Test Modules or contact our experts for a tailored recommendation.

Why is vacuum testing preferred for industrial applications?

Vacuum leak testing is often favored over atmospheric pressure methods because tracer gases move faster in vacuum.

This leads to:

  • Faster response times
  • Shorter cycle times
  • Higher sensitivity for small leaks

What leak detectors does Pfeiffer offer?

We offer a full range of leak detection technologies – from tracer gas systems to air-based testers – to meet diverse requirements in sensitivity, speed, and integration.

1. Tracer gas leak detectors (helium/hydrogen)
Used for high-sensitivity, quantifiable leak testing in safety-critical applications.


  • ASI 35 – Modular and flexible for system integration.
  • ASM 340 – Versatile for a broad range of industrial uses.
  • ASM 310 – Compact and portable for mobile or on-site testing.
  • ASM 390 – Rapid pump-down and short response times for large test objects.

2. Quadrupole mass spectrometry (QMS)
For gas analysis and detection at very low pressures or in complex environments.

  • PrismaPro: Compact, modular, ideal for integration into analytical systems.

3. Air-based leak testers
Cost-effective alternatives where extreme sensitivity is not required.
  • E2/VE2 – Multi-purpose and economical.
  • E-PDQ – Compact and easy to integrate.


Want to go deeper into specific technologies? Learn more about leak detection technology.

What accessories help optimize helium leak testing?

The right tools can make helium leak detection more precise and efficient.

Key accessories include:

  • HeliSpray: A refillable spray unit for accurate helium application on seals, valves, and welds.
  • Low-flow spray guns: Ensure controlled helium release, reducing false signals and improving detection accuracy.
  • Transport carts and boxes: Protect and mobilize your leak detectors and sensitive components.
  • Modular trolleys: Ideal for flexible test setups in laboratories or production environments.

What vacuum technology and accessories are used in leak testing?

Efficient and precise leak testing depends on a reliable vacuum setup. Pfeiffer Vacuum+Fab Solutions provides a full portfolio of vacuum pumps and accessories that support both stand-alone detectors and integrated systems.

Vacuum pumps

Enable fast evacuation and stable test conditions for tracer gas methods.

Accessories for test accuracy and control

Ensure environmental stability, signal reliability, and repeatable results.

All components are built to integrate seamlessly with our leak detectors and test systems.

How can I optimize integral leak testing for speed and performance?

Speeding up leak testing and maintaining sensitivity requires a well-tuned system. The choice between partial-flow and full-flow setups plays a key role.

System design tips for faster leak testing

  • Use short, wide piping to reduce conductance losses.
  • Select high-performance vacuum pumps to shorten evacuation times.
  • Choose fast-response detectors and adapt test modes (e.g. “normal” vs. “high-sense”).
  • Keep internal volumes low through compact layouts.
  • Apply nitrogen purge and minimize desorption for cleaner signals and lower background levels.
  • Thorough tracer gas background/contamination management, e.g. post evacuation of parts, exhaust lines.
  • Avoid gas liberation during outgassing by conditioning the test specimen beforehand.
  • Configure parallel or in-series vacuum pumps for higher throughput.

Full flow vs. partial flow: What to use when

Flow type
Best for
Key benefits
Full flow
Small volumes, very low leak rates, high precision
Strong signal, low background, high accuracy
Partial flow
Large volumes, time-critical tests, higher leak rates
Faster response, improved process stability

Full flow routes all tracer gases through the detector – ideal for sensitivity.
Partial flow
splits the gas stream – ideal for speed and scalability.

Why to choose Pfeiffer as a partner?

With over 60 years of experience in leak detection and decades of expertise in vacuum technology, Pfeiffer is your trusted partner for complete leak testing solutions. Our portfolio includes tracer gas and air-based leak detectors, high-performance vacuum pumps, and all essential components such as chambers, valves, and gauges.

Beyond hardware, our global service network and application laboratories offer comprehensive leak testing services, including feasibility studies, system optimization, and on-site support. We help you select the most efficient methods, define suitable leak rates, and tailor your system setup – ensuring reliable performance wherever your production is located.

Webinars about leak detection

​​Speed Up and Streamline: Optimizing Automotive Leak Testing

​​Speed Up and Streamline: Optimizing Automotive Leak Testing

​​Discover how to improve the leak testing process in terms of overall cycle time and cost drivers! Enriched with real-world examples.

Stay Cool: Sustainable Leak Testing in the HVAC-R Industry

Stay Cool: Sustainable Leak Testing in the HVAC-R Industry

Learn​ how to improve your leak testing by selecting the right vacuum pumps and adjusting parameters to achieve faster cycle times and cost savings.

Outdated to Optimized – Upgrade Your Coater or Vacuum Furnace

Outdated to Optimized – Upgrade Your Coater or Vacuum Furnace

Learn how targeted upgrades to vacuum equipment for coaters can boost efficiency, cut costs, and enhance quality – without replacing your entire setup.

Leak Testing of Hermetically Sealed Objects – Revealing the Secrets

Leak Testing of Hermetically Sealed Objects – Revealing the Secrets

Leak testing of hermetically sealed components has several secrets to performing and evaluating the measurements – we will reveal them!

Hidden Leaks, Hidden Costs: Detect Leaks and Save Money

Hidden Leaks, Hidden Costs: Detect Leaks and Save Money

Learn how to identify leaks, understand their multiple impacts and calculate their costs. Our experts will share real-life examples with you.

5 Ways to (Not) Destroy Your Leak Detector

5 Ways to (Not) Destroy Your Leak Detector

​What are the parts that make up a leak detector and what do you have to bear in mind when using it?

​​​Helium Spraying Demystified: Your Leak Test Questions Answered

​​​Helium Spraying Demystified: Your Leak Test Questions Answered

Learn more about best practice using a leak detector in a spray test of a vacuum system. Use of accessories and auxiliary pumps is demonstrated.

Become a Leak Detective: Pro Tips for Vacuum System Leak Detection

Become a Leak Detective: Pro Tips for Vacuum System Leak Detection

Ready to master leak detection in vacuum systems? Learn more about the basic methods and how to apply them efficiently in your daily work!