Vapor Intrusion Sampling Solutions

Significance of the Topic

Vapor intrusion presents a critical pathway by which subsurface volatile chemicals may enter indoor environments, posing health risks to occupants.
Accurate assessment of soil gas is essential for reliable evaluation of contamination and mitigation strategies.

Objectives and Overview of the Study

The primary objective of the presented solution is to deliver a universal, all-in-one soil gas sampling system that preserves sample integrity, supports a wide range of compounds and concentrations, and streamlines field procedures.
The overview covers sampling beneath building slabs, vadose zone monitoring, surface flux measurements and permanent well installations using a modular design.

Methodology and Instrumentation

Sampling is performed by collecting soil gas in Silonite™ coated stainless steel canisters, eliminating the need for pumps, batteries or adsorbent media selection.
Flow control and recovery are optimized by:

• Ensuring inert surfaces throughout the sample train to minimize adsorption and outgassing.
• Minimizing tubing length and surface area to reduce dead volume and carryover.
• Using precision orifices and flow regulators to maintain stable flow rates and avoid phase disturbance.
• Implementing leak-tight connections and triple-seal sub-slab sampling fittings to isolate target zones.

Testing protocols include pre-purge checks, tracer gas verification and shut-in leak tests under vacuum.

Used Instrumentation

• Chameleon™ soil gas sampling train with configurable inlets/outlets and flow rates (10–200 cc/min)
• Silonite™ coated stainless steel MiniCan™ canisters (600 mL to 1.4 L)
• Slab-Tight™ sub-slab sampling bonnet and mechanical anchor system
• Tracer gas shroud for helium or butane leak verification
• Down-hole vacuum gauges and 5 µm inlet filters
• Helium analyzer for tracer gas concentration monitoring

Main Results and Discussion

Field implementations demonstrated that canister sampling:

• Maintains sample integrity across variable humidity and temperature conditions.
• Avoids contamination associated with grouts or plastic tubing.
• Ensures reproducible recovery of volatile organics and semi-volatiles in diverse subsurface environments.
• Streamlines field operations by reducing equipment needs and allowing rapid deployment.

The modular approach facilitates multiple sampling techniques—static or dynamic flux, sub-slab intrusion and well monitoring—in a single sample train.

Benefits and Practical Applications

The described sampling system offers:

• Universal applicability across contamination levels and compound classes.
• Enhanced accuracy and minimized carryover for regulatory compliance.
• Reduced field complexity with battery-free, media-free canister capture.
• Compatibility with long-term monitoring programs, indoor air quality assessments and vapor intrusion mitigation verification.

Future Trends and Potential Uses

Emerging directions include:

• Integration of real-time sensors and automated flow control for adaptive sampling.
• Wireless data logging and remote validation of field test parameters.
• Advanced materials for further reducing background contamination and enhancing recovery.
• Broader adoption in environmental forensics, remediation projects and indoor air quality standards.

Conclusion

The all-in-one soil gas sampling solution presented by Entech Instruments significantly improves the reliability and efficiency of vapor intrusion studies.
By leveraging inert sample trains, configurable components and rigorous quality controls, this methodology advances contaminant assessment and supports informed decision-making in environmental and occupational health contexts.

Reference

No formal literature list was provided in the source document. The repository of technical details originates from Entech Instruments application notes (2019).