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Chemical Risk Assessment Tools

Draft Vapor Intrusion Screening Level Calculator Home Page (August 2017)

This figure depicts the migration of vapors in soil gas from contaminated soil and groundwater into buildings. Vapors in soil gas are shown to enter buildings through cracks in the foundation and openings for utility lines. Atmospheric conditions and building ventilation are shown to influence soil gas intrusion.


Welcome to the "Vapor Intrusion Screening Level (VISL) Calculator Home Page for Chemical Contaminants at Superfund Sites". This website was developed with DOE's Oak Ridge National Laboratory (ORNL) under an Interagency Agreement. The VISL website is now the source of screening levels for all the EPA regions. The VISL calculator output provides comparison values for residential and commercial/industrial exposures to soil gas, air, and groundwater. The VISL calculator output also provides risk estimates for residential and commercial/industrial exposures to soil gas, air, and groundwater. The unified use of the VISLs, to screen chemicals at Superfund sites, promotes national consistency. The VISL uses the same database of toxicity values, chemical parameters, and inhalation exposure equations as the Regional Screening Levels (RSLs) for Chemical Contaminants at Superfund Sites. Here you will find a calculator where default parameters can be changed to reflect site-specific risks. To ensure proper use of the calculator, please review the What's New, User's Guide, and Frequently Asked Questions links. Below is a general description of screening levels for chemical contaminants. If the calculator is used with non-default inputs in a decision on a Superfund site, it is recommended that the inputs be clearly identified and justified by the user.


Superfund sites are addressed under the authority of the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA) of 1980, which was amended by the 1986 Superfund Amendments and Reauthorization Act. The purpose of this website is to provide a screening level calculation tool to assist risk assessors, remedial project managers, and others involved with risk assessment and decision-making at CERCLA sites in developing or refining screening levels.

This tool is based on the vapor intrusion guidance presented here. Vapor intrusion occurs when there is a migration of vapor-forming chemicals from any subsurface source into an overlying building. Recognition of soil vapor intrusion to buildings and other enclosed spaces occurred in the 1980s with concerns over radon intrusion. Subsequently, there was an increasing awareness that anthropogenic chemicals (e.g., petroleum hydrocarbons and chlorinated solvents) in soil, groundwater, and sewers and drainlines could also pose threats to indoor air quality via the vapor intrusion pathway.

Radionuclides are not addressed on this website. For radionuclide vapor intrusion please go to EPA's Radon Vapor Intrusion Screening Level Calculator.

Note: No consideration is given to ecological effects in the values presented in this calculator.