蒸汽侵入-建筑物下方（或附近）受污染的地下水或土壤导致的结构中存在潜在有毒蒸汽-可能导致健康问题和法律暴露。如果你是房地产开发商或住宅，商业或工业产权所有者，还没有处理蒸汽入侵，机会是你会很快，特别是在城市地区的物业。近年来，环境尽职调查过程的演变和精明贷款人的要求导致了对蒸汽入侵可能性的更大认识，在某些情况下，需要缓解实际或潜在的蒸汽入侵。

Increasingly, vapor intrusion issues are being flagged in Phase 1 Environmental Site Assessment reports, essentially during refinancing or property acquisitions. Some States have little regulatory guidance on how to address potential vapor issues, and others have prescriptive protocols to evaluate and address vapor concerns. Developers and builders applying for a financing from most lending institutions are now likely to encounter requirements for due diligence relating to vapor intrusion.

蒸汽入侵：一个日益引起关注的问题

人类直接接触蒸汽；如果建筑物中有蒸汽侵入（VI），居住者只需呼吸即可受到影响。然而，大多数与蒸汽侵入有关的化学物质不会立即对建筑物的居住者造成明显的症状。相反，长期、低水平的慢性暴露于未被发现的蒸汽中会导致从神经系统疾病、精神混乱到癌症等各种问题。

VI可能来自建筑物下方或现场的化学品，这些化学品来自过去的工业活动，或者来自地下水流中迁移到现场的其他财产的化学品。蒸汽可以通过楼板或墙体裂缝、楼板中未密封的施工缝、公用管线或地漏等进入建筑物。在一些建筑物中，由于风和温度的变化，通过结构的“烟囱效应”可以增强蒸汽的运动。

Due Diligence

The most common first step in identifying a potential VI concern is to complete a Phase I ESA, a fairly well-established process that involves looking at the history of the property, previous operations, and the types of chemicals that may have used at the site.

第一阶段ESA还包括搜索现场或现场规定半径内可能记录的泄漏或释放记录。审查的典型记录包括泄漏地下储罐设施的清单、报告的泄漏清单以及由于检测到土壤或地下水中的污染物以及最近污染的土壤蒸汽而进入州清理计划的财产清单。

关注的化学品

美国环保署已经确定了大约180种化学品，这些化学品对潜在的有害蒸汽入侵有影响。这些通常是挥发性有机化合物，或挥发性有机化合物，具有足够的挥发性和潜在的吸入毒性。

Many VOCs are used in industry, but many are found in common household products. For example, benzene and toluene are components of gasoline, which many of us have in our garage for use with a lawn mower. Trichloroethylene, or TCE, is a common cleaning solvent used in industry, but it’s also found in spot removers or other cleaning agents that you might use in your garage or in the laundry room. Perchloroethylene (PCE, or perc) is a dry cleaning solvent; clothes in your home that are fresh from the dry cleaner may have some residues of perc on them. EPA has documented that these chemicals are routinely found in homes and workspaces.

Sampling and Detection

如果有理由怀疑建筑物内有蒸汽侵入的可能性，下一阶段需要收集样本。这一过程通常从环境介质样本开始，以确定挥发性有机化合物（土壤、地下水、土壤蒸汽）。目前，在室内空气采样不足的情况下，土壤气体采样被认为是评价VI潜在污染最有效的方法。然而，众所周知，土壤蒸汽在空间和时间上都是可变的，因此从业者需要考虑有多少样本以及在什么时间段内。答案可能会随着年龄和结构的使用、挥发性有机化合物来源的性质以及潜在受体的敏感性而变化。这就是从业者的判断和监管者的要求可以发挥很大作用的地方。

Indoor air sampling is obviously the best method to determine if a VI issue exists, however even this straightforward approach has pitfalls since VOCs can vary dramatically over time based upon a variety of factors. And, data may be skewed by ambient concentrations of household chemicals in the structure as described earlier.

Mitigation

If vapor intrusion is detected in a structure, there are a variety of approaches to address the problem.

In some structures, vapor can enter through a multitude of channels, and a common approach is to try and eliminate those obvious pathways before considering more disruptive techniques. Floor joints, sumps, utility conduits, floor drains, and slab penetrations are all suspect pathways that need to be considered. If sealing of entry points is unsuccessful, the professional can consider several other mitigation approaches that will be very much both site and cost dependent.

Conclusion

Increasingly, as the real estate industry becomes more attuned to the issue VI and states adopt guidance and regulations, vapor intrusion is becoming a concern for owners, developers, builders and lenders. Proactively managing this issue is best tackled using a methodical approach to assess source, migration and mitigation options. Braun Intertec professionals have been addressing vapor intrusion and designing vapor mitigation systems for over 25 years.

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