Vapor intrusion into structures on a property can potentially create significant liability for property owners and prospective purchasers and have a material impact on property value. As such, it is a growing concern in property environmental due diligence associated with real estate transactions (Buonicore and Crocker 2005; Buonicore 2007). On March 3, 2008, ASTM (2008) published E 2600-08, Standard Practice for Assessment of Vapor Intrusion into Structures on Property Involved in Real Estate Transactions. Based on feedback from the marketplace after almost nine months of use, a number of revisions have been proposed to improve the standard. Use of the standard in the field since its passage identified a number of revisions to improve the standard. These revisions can be divided into three categories: technical, legal, and clarification. Two technical revisions have been proposed, both involving Tier 1 methodology: Differentiate in Tier 1 between what should be done if ground water flow direction is not able to be estimated (in the Phase I investigation) and when it can be estimated. Eliminate the secondary area of concern (AOC) in Tier 1. Field experience to date has shown it not to be necessary and that it can waste considerable time and money investigating sites a considerable distance from the target property (TP) that are highly unlikely to result in a vapor intrusion problem. Four revisions have been proposed by the legal community. These include: Redefine that a potential vapor intrusion condition (pVIC) identifies only the potential for vapors to reach the subsurface of the TP, which does not without further investigation necessarily result in an indoor air quality problem (i.e., a vapor intrusion condition, or VIC). To evaluate whether or not a VIC exists is the purpose of the Tier 3 investigation, and for that the standard directs the user to applicable federal or state guidance, policy, or regulation. Indoor air quality assessment is a nonscope consideration in E 1527. A Phase I under E 1527 would not include an assessment of whether vapors potentially reaching the TP’s subsurface could migrate into a structure on the TP and cause an indoor air quality problem, i.e., create a VIC. Such a determination would require a VIC assessment (as identified in Tier 3). A pVIC should not automatically result in a recognized environmental condition (REC) on the TP. Any such determination is the responsibility of the environmental professional. Rather than presuming that a pVIC exists if it cannot be ruled out by screening, E 2600-08 should be revised to state instead that the screening cannot rule out the possibility of a pVIC, but further investigation would be necessary. Six revisions have been proposed for clarification purposes. Clarify that the prescriptive part of the standard, Tiers 1 and 2, constitute vapor intrusion (VI) screening, which is only a part of the VI assessment process associated with a real estate transaction. E 2600-08 should clearly differentiate between VI screening and VI assessment. The E 2600-08 standard is effectively a VI screening standard for real estate transactions to eliminate sites where VI is unlikely. If a site cannot be screened out, it means that additional information and investigation may be necessary to assess the issue (much the same as a Phase II might be conducted to investigate a REC identified in a Phase I). Reword what specifically is required under Tier 1 and Tier 2 so that it is easier to understand. In Tier 1 clarify that the “source” is the property where the contamination originated. There has been confusion in the field associated with contaminated groundwater or soil being viewed as the source since the vapors are actually off-gassed from these media. The standard should distinguish between a primary source (e.g., a drycleaner) and a secondary source (e.g., contaminated groundwater). The standard includes a flow chart of the vapor intrusion assessment process, but does not include a flow chart of the Tier 1 and Tier 2 screening process, and it should. Clarify that there must be evidence of contamination above regulatory acceptable levels at a source property in the AOC for it to be considered in the screening. Such evidence can be either direct or indirect (such as where experience has shown a high probability for contamination, e.g., a drycleaners). Clarify that if there are preferential pathways (natural or man-made), Tier 2 invasive sampling may be required to assess if a pVIC exists. These revisions will be balloted in February and March 2009 and discussed at the April 2009 Task Group meeting. There will be another ballot in summer 2009. It is anticipated that the revised standard should be approved by the Task Group at its October 2009 meeting and published by ASTM at the end of the year.