| a.k.a.: | Abbreviation for "also known as"; synonym for "alias." |
| A.S.A.: | Abbreviation for "assistant state's attorney." An assistant state's attorney, acting on behalf of the state's attorney, represents the state in criminal proceedings. In Cook County, an assistant state's attorney must review all felony charges before they are approved. |
| A/O: | Abbreviation, often used in case reporting, for "arresting officer." |
| Above-ground storage tank: | Storage tank that is not buried. Compare Underground storage tank. Unburied tanks are more prone to physical damage, and leaks are released to the air or ground, rather than the soil surrounding a buried tank. |
| Accelerant: | Flammable fuel (often liquid) used by some arsonists to increase size or intensity of fire. May also be accidentally introduced when HAZMAT becomes involved in fire. |
| Accountability: | The process of emergency responders (fire, police, SAR, emergency medical, etc...) checking into and making themselves announced as being on-scene during an incident to an incident commander or accountability officer. Through the accountability system, each person is tracked throughout the incident until released from the scene by the incident commander or accountability officer. This is becoming a standard in the emergency services arena primarily for the safety of emergency personnel. This system may implement a name tag system or personal locator device (tracking device used by each individual that is linked to a computer). |
| Admission: | A person's acknowledgment of his/her involvement in criminal behavior, but not in itself sufficient to establish guilt. Example |
| AFA: | Automatic Fire Alarm/Actuating Fire Alarm |
| Aggravated (offense; e.g. aggravated assault, aggravated battery): | A condition which makes an offense more serious, and subjects the offender to greater punishment. Example |
| Alarm: | (1) system for detecting and reporting unusual conditions, such as smoke, fire, flood, loss of air, HAZMAT release, etc; (2) a specific assignment of multiple fire companies and/or units to a particular incident, usually of fire in nature; (3) centralized dispatch center for interpreting alarms and dispatching resources. See fire alarm control panel. |
| All companies working: | Status report at fire scene indicating that available manpower is busy, and more resources may become necessary if incident is not controlled soon. |
| Ammonium nitrate: | Component of ANFO; contents of two ships that exploded in Texas City Disaster, killing over 500 people, including all 28 volunteer firefighters at the scene. |
| ANFO: | Ammonium Nitrate Fuel Oil combination making a high explosive. |
| Apparatus: | A term usually used by firefighters describing a piece of equipment, usually a company vehicle. |
| Area: | A group of five police districts which share a detective unit, a youth investigation unit, and male and female lock-up facilities. Chicago is divided into five areas. |
| Arrest: | To take a person into custody, by authority of law, for the purpose of charging him/her with a criminal offense. An arrest is proper when an officer observes criminal behavior or reasonably believes the individual has engaged in criminal behavior; or upon warrant issued by a judge or magistrate. |
| Arson: | The crime of maliciously (or perhaps recklessly) setting fire to property, especially a dwelling. Punishable in various degrees, depending upon the circumstances. Occasionally occurs as a psychotic act of a mentally ill firefighter. |
| Arson: | Unlawfully damaging real or personal property by means of fire or explosives. The property must have a value of $150 or more. This offense includes damaging one's own property with the intent to defraud an insurer. |
| Assault and Battery: | Two distinct offenses which can occur independently or together. Assault is placing someone in reasonable apprehension of a battery, e.g. by making threatening statements or raising a fist. Battery is causing bodily harm to a person by any means, or making physical contact with a person of an insulting or provocative nature. |
| Authority Having Jurisdiction (or AHJ): | Organization or agency with legal authority over a given type of incident (e.g, fire, EMS, SAR, arson, HAZMAT); may change or overlap as incident changes, as where fire becomes arson investigation once danger is over, or Motor Vehicle Accident becomes police business after vehicle extrication, fire, and HAZMAT issues are complete. |
| Autoextended fire: | Structure fire that has gone out a window or other opening on one floor and ignited materials above, on another floor or other space (attic, cockloft). |
| Available flow: | Total amount of water that can be put on a fire, depending upon water supply, pump size, hoses, and distance to the fire. IC must assess available flow to determine whether additional apparatus or streams are required. See Fire flow requirement. |