Great Question: A Manufacturing Podcast Capturing the Invisible: Best Practices in Gas Grab Sampling
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Nov 15, 2025 
Matthew Dixon, Swagelok's global technical lead for grab sampling, brings over 27 years of expertise to the table. He dives into the complexities of gas grab sampling, explaining the unique challenges it presents compared to liquid sampling. Matthew covers key system components for accuracy and safety, practical field mistakes to avoid, and the importance of representativeness in gas samples. He also discusses the evolving role of automation and online analyzers, emphasizing that there's still a vital need for traditional grab sampling.
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Compressibility Creates Time Delays
- Gas compressibility creates time delays because packed molecules take longer to move through sampling lines.
- Condensation risk means keep gas hot or reduce pressure to avoid phase change during transport.
Use Proper Cylinders And Safety Devices
- Use stainless steel sample cylinders in vertical orientation and fill from the top down to flush particulates and condensate.
- Fit cylinders with rupture discs or relief valves to protect against overpressure.
Keep Phases Separate And Minimize Mixing Volumes
- Separate any liquids before the gas sample reaches the analyzer using knockout pots or membrane separators.
- Minimize mixing volumes like large knockout pots to avoid long flush times.