Research has shown that exposure to contaminants by breathing the indoor air often is a greater health threat than direct contact to contaminants in the soil or from drinking contaminated groundwater. For that reason, the cleanup standards set by the Massachusetts Department of Environmental Protection (DEP) are very conservative. Other nearby states similarly have regulatory requirements to protect residents. In Massachusetts, the Massachusetts Contingency Plan (MCP) regulations dictate that Licensed Site Professionals (LSPs) – professionals trained and licensed by the state to oversee site cleanups – consider indoor air contamination as part of the site closure process. These regulations have led to a vast increase in the need for SSDSs over the past several years.