In accordance with the National Environmental Policy Act of 1969 (NEPA), the DHS procedures for implementing NEPA (DHS Directive 023-01 Rev 01, Implementation of the National Environmental Policy Act), and the Council on Environmental Quality (CEQ) regulations for implementing the procedural provisions of NEPA (40 CFR Parts 1500-1508), the Department of Homeland Security has prepared a Draft Environmental Assessment (DEA) to evaluate the potential impacts to the human environment resulting from an airflow study throughout portions of the New York City subway system. The study is intended to gather data on the behavior of airborne contaminants if they were to be released into the subway. The proposed tests, scheduled for May 9 – 13, 2016, will include release of non-toxic, inert, odorless gas and particle tracers into the subway system and include sampling in various locations in the system. DHS reviewed the comments received during the public comment period and has prepared a Final Environmental Assessment (EA). On April 20, 2016 DHS made a Finding of No Significant Impact (FONSI) and has concluded the NEPA review for this action. The Final EA and signed FONSI are available for download.