So, who is responsible for mitigating this soil vapor intrusion? The New York State Department of Environmental Conservation (DEC) describes the conditions under which the state will conduct the vapor intrusion evaluations and the order in which the sites will be assessed. If exposures represent a concern due to indoor sources, then the state will provide guidance to the property owner and/or tenant on ways to reduce their exposure. If exposures represent a concern due to outdoor sources, then DEC will decide who is responsible for further investigation and any necessary remediation. Depending upon the outdoor source, this responsibility may or may not fall upon the party conducting the soil vapor intrusion investigation.