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Leak Testing Examinations

About Leak Testing (LT)

Leak Testing is used to detect through leaks using one of the four major LT techniques: Bubble, Pressure Change, Halogen Diode and Mass Spectrometer Testing.

  • Bubble Leak Testing relies on the visual detection of a gas (usually air) leaking from a pressurized system; Pressure Change Leak Testing can be performed on closed systems only-- detection of a leak is done by either pressurizing the system or pulling a vacuum then monitoring the pressure. 
  • Halogen Diode Leak Testing is done by pressurizing a system with a mixture of air and a halogen-based tracer gas-- after a set period of time, a halogen diode detection unit, or "sniffer", is used to locate leaks. 
  • Mass Spectrometer Leak Testing can be done by pressurizing the test part with helium or a helium/air mixture within a test chamber then surveying the surfaces using a sniffer, which sends an air sample back to the spectrometer.

Topical Outline

This examination is 4 hrs in length, having 135 questions of equal value.

  1. Principles theory
    • Physical principles in leak testing
    • Principles of gas flow
    • Proper selection of LT as method of choice
  2. Equipment/Material
    • Leak testing standards
    • Detector/instrument performance factors
    • Vacuum pumps
    • Bubble testing practices and techniques
    • Absolute pressure testing equipment
    • Absolute pressure hold testing of containers
    • Absolute pressure leakage rate testing of containers
    • Analysis of data for determination of accurate results
    • Halogen testing equipment
    • Helium mass spectrometer testing equipment
  3. Technique/Calibration
    • Bubble test
    • Pressure change/measurement test
    • Halogen diode detector leak test
    • Mass spectrometer leak testing
    • Helium mass spectrometer vacuum testing by dynamic method
    • Helium mass spectrometer vacuum testing by static method
  4. Interpretation/Evaluation
    • Basic techniques and/or units
    • Test materials and equipment effects
    • Effects of temperature and other atmospheric conditions
    • Calibration for testing
    • Probing/scanning or measurement/monitoring
    • Leak interpretation evaluation
    • Acceptance and rejection criteria
  5. Procedures
  6. Leak testing procedures
  7. Leak testing specifications
  8. Safety and Health
    • Safety considerations
    • Safety precautions
    • Pressure precautions
    • Safety devices
    • Hazardous and tracer gas safety
    • Types of monitoring equipment
    • Safety


The number in parentheses following each reference is the ASNT catalog number.