ILEAS (Illinois Law Enforcement Alarm System) is a system of mutual aid police agencies that respond when large police action is needed for public safety emergencies and crowd control. Northwest Central Dispatch System in Arlington Heights is the primary dispatch center for ILEAS.
Compare ILEAS to NIPAS (Northern Illinois Police Alarm System), which is a mutual aid organization of police departments that consists of a Mobile Field Force for civil disturbances, and an Emergency Services Team for hostage/barricade incidents, high-risk warrant service, major crime scene searches, search and rescue missions, dignitary protection, and similar tactical incidents.
Mission: ILEAS Mutual Aid Response Teams, also recognized as Mobile Field Forces, provide a rapid, organized and disciplined response to civil disorder and public safety emergencies that may occur during distribution of pharmaceuticals from the National Strategic Stockpile, weapons of mass destruction incidents, emergency situations, including natural or man-made disasters of various types, and routine local and statewide mutual aid which exceeds the effective ability of local enforcement.
Function: The Mobile Field Force is designed to provide rapid, organized and disciplined response to civil disorder, crowd control or other situations. Mobile Field Forces are formally structured teams based on a platoon of law enforcement officers from multiple agencies with an assigned leader. Tactics used are based on small squad tactics developed by the Office of Domestic Preparedness as well as the more traditional Mobile Field Force and general police patrol tactics. Officers are from ILEAS member agencies.
— ILEAS website (April 7, 2017)