Draft Radon Vapor Intrusion Screening Level Calculator Home Page

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


Welcome to the "Radon Vapor Intrusion Screening Level (RVISL) Calculator Home Page for Radionuclide Contaminants at Superfund Sites". This website was developed with DOE's Oak Ridge National Laboratory (ORNL) under an Interagency Agreement with the U.S. Environmental Protection Agency (EPA). The RVISL website is now the generally recommended source of radon screening levels for all EPA regions. The RVISL calculator output provides comparison values and risk and dose estimates for residential and commercial/industrial exposures to radon in soil gas, air, and groundwater. Note that for Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) remedial actions, dose assessment is generally done only to show compliance with a dose-based Applicable or Relevant and Appropriate Requirement (ARAR). In addition, the calculator presents the option to compare the indoor air concentration, entered by the user or derived from groundwater or soil gas activities, to state standards or Uranium Mill Tailings Radiation Control Act (UMTRCA) standards, which also may be potential ARARs. The unified use of the RVISLs to screen radon at Superfund sites promotes national consistency. The RVISL uses the same database of toxicity values, chemical parameters, and inhalation exposure equations as the Preliminary Remediation Goals (PRGs) for Radionuclide Contaminants at Superfund Sites calculator. The RVISL calculator provides default parameters that can be modified 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. The EPA has prepared a fact sheet for the general public that describes RVISL uses, RVISL calculator operation, and land uses available for assessment. Additionally, this fact sheet describes the RVISL content in greater detail for EPA staff. Below is a general description of screening levels for radon. 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.

The RVISL calculator provides updated guidance for developing screening levels (SLs) or preliminary remediation goals (PRGs) for indoor radon-222, radon-220, and radon-219 that are risk- or dose-based and for showing compliance with the UMTRCA indoor radon standards for radon-222 and radon-220. The RVISL, therefore, supersedes the risk assessment approach in Preliminary Remediation Goals for Radionuclides in Buildings (BPRG) electronic calculator, the dose assessment approach in ARAR Dose Compliance Concentrations Goals for Radionuclides in Buildings (BDCC) electronic calculator, and Q17 of the guidance document "Radiation Risk Assessment At CERCLA Sites: Q & A" issued on May 2014. Computer codes such as the RVISL, which were developed to predict potential human exposure from radon concentrations in indoor air, are based on simplified equations and assumptions and are highly imprecise for an individual house or structure. EPA would recommend, where possible, Regions use measurements of radon indoors rather than rely on the transport portions of the RVISL. In particular, testing of groundwater or soil gas is not required to demonstrate compliance with RVISL WL, pCi/L, risk, or dose targets.

Users should note that since background radon levels are typically outside the risk range, the RVISL calculator is likely to be used primarily for ARAR compliance. For example, the UMTRCA indoor radon standards 40 CFR 192.12(b)(1) and 192.41(b) were identified as likely Federal ARARs for Rn-222 and Rn-220 in Attachment A of the EPA guidance document "Establishment of Cleanup Levels for CERCLA Sites with Radioactive Contamination." There are some state standards expressed in pCi/l or mrem/yr that, if more stringent than the UMTRCA standards, may be selected as ARARs.


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.

Rn-222 is commonly refered to radon because of its parent radium-226. Rn-220 is commonly called thoron because of its parent thorium. Rn-219 is commonly called actinon because of its parent actinium. Click the decay chain link to see the decay series for Rn-222, Rn-220, and Rn-219. See section 2.2 of the User's Guide to learn what progeny are evaluated in this web calculator. More details about the decay chains can be found in the EPA's Decay Chain Tool.

This tool is based on the Technical Guide for Assessing and Mitigating the Vapor Intrusion Pathway from Subsurface Vapor Sources to Indoor Air (June 2015). Vapor intrusion occurs when there is a migration of vapor-forming chemicals or radon 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.

The RVISL calculator results were previously verified. The documentation from these may be seen on the Internal Verification and External Verification pages. The RVISL calculator was also previously peer reviewed, and the documentation of the review may be seen here.

Chemicals are not addressed on this website. For chemical vapor intrusion, please go to EPA's Vapor Intrusion Screening Level Calculator.

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