Vapor Intrusion Monitoring
Vapor Intrusion Defined
Vapor intrusion (VI) occurs when volatile chemicals in buried wastes
and/or contaminated groundwater emit vapors that migrate through
subsurface soils and into indoor air spaces of overlying buildings.
This can result in an indoor air quality problem.
Sampling at the Source - Soil
Soil Gas Sampling
Because soil is the pollutant pathway, many vapor intrusion studies
include a soil study. Soil gas sampling results can identify underground
contamination and trace the source, extent, and movement of pollutants.
Typical soil gas sampling includes driving a hole into the ground
and inserting a probe into the hole. The air sample is pulled through
the probe and collected into a container. U.S.
EPA Standard Operating Procedure (SOP) # 2042 for Soil Gas Sampling specifies
Tedlar® sample bags as containers and the use of negative-pressure
sampling
for soil gas collection. A sample bag is placed in an airtight
chamber and a sample pump is used to create a vacuum in the chamber.
This causes the air sample to enter into the bag without going through
the pump; this method eliminates contamination of the sample and
the pump. Stainless steel canisters may also be used as containers.
Samples are analyzed in the field using direct-reading instruments
and/or sent to a qualified laboratory for analysis.
SKC Sampling Equipment for EPA SOP 2042
Sampling in the Overlying Structure
Vapor Intrusion Monitoring
Indoor air sampling in vapor intrusion
studies has been performed typically with 6-liter stainless steel
canisters
to
collect ppb-level
VOCs. U.S. EPA validated sampling and analytical methods TO-14A
and TO-15 specify stainless
steel canisters. However, passive samplers are emerging as a cost-effective
alternative to canisters. A side-by-side
study shows SKC Ultra Passive
Samplers to have good correlation with canisters. Ultra Passive
Samplers are smaller, less expensive to ship, and their
lower cost allows more samples to be collected. Ultra samples are
thermally desorbed for sub-ppb level detection of many VOCs.
Stainless Steel Canisters: The Traditional Approach
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Ultra Passive Samplers: The New Approach |
- Canister vacuum pulls the air sample without use of batteries
or AC power
- Flow restrictors maintain flow stability over the desired
time period from < 1 minute to 12 hours
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- Collect samples for low ppb to ppt-level measurements
- Easy, cost-effective alternative to canisters
- Side-by-side study with canisters shows good correlation
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SKC Ultra I Passive Samplers
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SKC Ultra II Passive Samplers |
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- Internal funnel for direct transfer to thermal desorption tube
- SKC Ultra I Passive Samplers contain thermally purged sorbent that is ready for immediate use within 30 days for low ppb-level measurements.
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- Internal funnel and built in vial adapter for easy filling
and emptying
- SKC Ultra II Passive Samplers are sold empty and are filled by the user with
purged sorbent (supplied in vials) for ppt-level measurements.
- See SKC
update to U.S. EPA Method TO-17 (PDF)
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Current Initiatives in Vapor Intrusion
ASTM International
ASTM E2600-08 Standard Practice for Assessment
of Vapor Intrusion into Structures on Property Involved in Real
Estate Transactions is a new standard to be used to perform vapor
intrusion
assessments on properties involved in real estate transactions.
ASTM E2600-08 can also be used as a voluntary supplement to Standard
Practice
E 1527 Phase 1 Environmental Assessment. This standard complements
existing state and federal vapor intrusion policy and guidance.
AIHA Task Force
A February 2007 Synergist article
reported that the AIHA® Environmental Issues Committee has begun
a vapor intrusion
project to monitor this focus area for industrial hygienists.
Laboratories
Laboratories for Analysis of Ultra Passive Samplers
Laboratories for Analysis of Canister Samples
Related Links
U.S.
EPA OSWER Draft Guidance for Evaluating the Vapor Intrusion to Indoor
Air Pathway from Groundwater and Soils (Subsurface Vapor
Intrusion Guidance, EPA530-D-02-004, Nov. 2002 )
U.S. EPA Fact Sheet: Evaluating the Vapor Intrusion into Indoor
Air, EPA530-F-02-052, Nov. 2002
New York State Department of Health - Guidance for Evaluating Soil
Vapor Intrusion in the State of New York, Oct. 2006
Washington State Department of Health - Environmental Health
Fact Sheet, March 2007
ASTM E2600-08 Standard Practice for Assessment of Vapor Intrusion
into Structures on Property Involved in Real Estate Transactions
Uncertainty and the Johnson-Ettinger Model for Vapor Intrusion
Calculations, EPA/600/R-05/110
U.S. EPA Method TO-14A Determination of VOCs in Ambient Air Using
Specially Prepared Canisters with Subsequent Analysis by Gas Chromatography
U.S. EPA Method TO-15 Determination of VOCs in Air Collected in
Specially Prepared Canisters and Analyzed by Gas Chromatography/Mass
Spectrometry (GC/MS)
U.S. EPA Method TO-17 (SKC Update)
Performance of SKC Ultra Passive Samplers
Containing Carboxen 1016, Carbotrap Z, or Chromosorb 106 When Challenged
With a Mixture Containing
Twenty of OSHA SLTC's Top Solvent Analytes - Search on "Ultra
Passive Sampler"
Vapor Intrusion Report - Capitol Press, LLC
Issues and Concerns in Diffusive Sampling: Factors Influencing Performance.
A Field Evaluation of Diffusive Samplers and Canisters For Monitoring
Volatile Organic Compounds in Vapor Intrusion Studies
Feasibility Of A New Diffusive Sampler To Measure Sub-ppb Levels
Of VOCs
Measuring Sub-ppb Levels of VOCs in Indoor Air: Performance Comparison
of Diffusive Badges and Canisters
This page was last modified April 4, 2008
