High Quality Content by WIKIPEDIA articles! The Emergency Service Unit (ESU) is the multi-faceted and multi-talented element within U.S. municipal, county, or state authority law enforcement agency`s Special Operations command. ESU`s exist mainly in the regional New York City Area but includes several jurisdictions outside the region. ESU is also synonymous with the term Emergency Services Squad (ESS) and Emergency Service Detail (ESD). The ESU operates at the direction of the command staff and responds to emergency and high-risk situations that occur outside the scope of duties of responding patrol and criminal investigation units. ESU members train continually both in-house, with other local, state, federal and military specialized units and sometimes members of a Federal Emergency Management Agency (FEMA) Urban Search & Rescue (USAR) Team.