“Vapor intrusion” refers to the process by which volatile chemicals move from a subsurface source into the indoor air of overlying or adjacent buildings.  The New York State Departments of Health (“NYSDOH”) and Environmental Conservation (“NYSDEC”) have identified vapor intrusion as a major concern and it has become a dominant issue in their oversight activities.  Moreover, because of the nature of sub-surface vapors, oftentimes vapor intrusion is not limited to on-site concerns but also to off-site impacts.

The NYSDOH adopted soil vapor intrusion guidelines that provide a basis for deciding how, where and when to conduct soil vapor intrusion evaluations and whether the sub-surface and indoor air sampling results fall within no action, monitoring or mitigation ranges.  The NYSDEC adopted a strategy for evaluating vapor intrusion at sites that are undergoing or have undergone remediation.

Almost any commercial, industrial or residential real estate transaction needs to take vapor intrusion into consideration as part of due diligence pre-purchase activities. This is particularly important if volatile chemicals, such as chlorinated solvents or petroleum-related compounds, were historically or currently used at the property.

Concerns about vapor intrusion led the New York legislature to enact a law in 2008 that requires property owners or owners’ agents (such as managing agents) to notify tenants and occupants about test results that exceed certain guidelines relating to indoor air contamination.  The statute is applicable only to vapor intrusion test results from certain specified entities, denominated as an “issuer” under the law. The tenant notification law requires that a notice be sent to tenants and occupants within 15 days after an “issuer” provides the owner or owner’s agent, (who themselves can be “issuers”), with test results that show exceedances of either the NYSDOH vapor intrusion guidelines or an Occupational Safety and Health Administration guideline for indoor air quality.  The law specifies the content of the notice.  The law also contains specific notice provisions applicable to prospective tenants, where the site has indoor air quality engineering controls or on-going monitoring of indoor air quality.