A Guide to Seattle Fire Department Response Codes and Unit Types
Published April 25, 2026 · 10 minute read
If you spend any amount of time watching the Seattle Breaking live feed, you'll quickly notice that Seattle Fire Department dispatches use a small vocabulary that repeats over and over. "Aid Response," "Medic Response," "Auto Fire Alarm," "Investigate Out Of Service," "MVI Freeway." The feed used more than 130 distinct type strings between October 2025 and September 2026, though a few dozen account for nearly all records, and once you know what they mean the feed becomes much easier to read. This is a quick reference written for residents, not for firefighters.
The categories at the top level
For our own categorization on the live feed, we group SFD calls into six visual buckets — fire, medical, traffic, hazmat, rescue, and other. SFD itself doesn't use those labels. SFD uses dozens of specific type strings, each of which maps in their CAD to a "response plan" — a pre-defined list of apparatus that gets sent. Understanding both the type string and the response plan is what tells you the actual scale of what is happening on the ground.
AID Response
"AID Response" is by far the most common type you'll see, accounting for roughly half of all Seattle Fire dispatch records. It is the catch-all label for an emergency medical call that does not rise to the level of a paramedic response. A typical AID Response sends a single Basic Life Support unit — an aid unit (a two-firefighter ambulance staffed by EMT-trained personnel) or an engine company — to a scene. The patient is assessed and either treated and released, treated and transported to a hospital, or upgraded to a medic response if the situation warrants paramedics.
If you hear an AID Response draw more than one unit on the scanner (an engine company plus an aid unit, for instance), that often means an engine was closer and was sent to begin assessment while the aid unit traveled from a farther station. The public dataset itself does not list responding units.
Medic Response
"Medic Response" is the paramedic-level upgrade. It dispatches one of Seattle's eight dedicated Medic units — staffed by two paramedics, not EMTs — plus typically an aid unit and sometimes an engine company. Medic Response is used for cardiac arrests, strokes, severe trauma, severe respiratory distress, and other Advanced Life Support (ALS) situations. Seattle Medic units are nationally recognized for cardiac arrest survival rates and the dispatch criteria reflect that — they are sent quickly and they are sent often.
MVI - Motor Vehicle Incident
"MVI - Motor Vehicle Incident" is a response to a reported vehicle collision; a related type, "MVI Medic," is used when the reported injuries call for paramedics. The presence of "MVI" in the type string tells you that the call originated from a collision report. Responses to these calls can include an aid unit, an engine company (for hazard control, fluid containment, and extrication if needed), and sometimes a ladder truck for heavy extrication or stabilization. If a freeway is involved, expect additional units staged for traffic control.
Auto Fire Alarm / Automatic Fire Alarm Resd
"Auto Fire Alarm" is an alarm-monitoring company calling in an alarm activation. It does not mean there is a fire. The vast majority of automatic fire alarm dispatches resolve as a non-fire activation — burnt food, a faulty smoke detector, construction dust, a triggered pull station. SFD response plans for an alarm vary by building type:
- Residential alarm — typically a single engine company. Often clears quickly once the crew confirms no fire.
- Commercial alarm — usually a larger assignment than a residential alarm, which can include a ladder truck.
- High-rise alarm — a heavier assignment of multiple engine and ladder companies plus a battalion chief. High-rise response is heavily weighted because vertical evacuation and standpipe operations are resource-intensive.
Fire in Building
"Fire in Building" is what it sounds like — a confirmed or suspected fire inside a building. A first-alarm building-fire response in Seattle brings multiple engine and ladder companies, medical units, and chief officers from several stations, adding up to dozens of firefighters. A working fire (one that is actively burning and requires interior firefighting) can escalate to additional alarms, each adding more companies.
If you see a Fire in Building on the live feed, the units listed on the dispatch are almost always more than the units that ultimately work the scene — many will be cancelled en route or staged. The dispatch type does not get downgraded if the fire turns out to be small.
Working Fire
"Working Fire" is a status change, not an initial dispatch. It is declared by the first arriving company officer when they confirm that a structure fire is actively burning and that interior firefighting will be required. A working-fire declaration typically brings additional companies and support resources to the scene. If you see "Working Fire" appear on the feed, the underlying incident has escalated significantly.
MVI Freeway / MVI Medic
"MVI" stands for motor-vehicle incident. The qualifiers tell you whether the collision is on a freeway and whether paramedics were needed. Freeway collisions typically draw an engine company in addition to an aid or medic unit because freeway responses require traffic protection — the engine functions as a steel barrier between traffic and crew. "MVI Medic" adds a paramedic unit for more serious injuries.
Investigate Out Of Service / Natural Gas Odor
Some types describe a unit checking something out rather than a confirmed emergency. "Investigate Out Of Service" is one of the more common types on the feed (about 2,000 dispatches a year), but the public dataset does not say what was investigated. "Natural Gas Odor" is a reported gas smell, and is separate from the much rarer "Natural Gas Leak." Response to these is usually a single company.
Rescue Calls — Water, Technical, Elevator
Seattle's geography produces a steady stream of rescue calls. Water rescues are common — Lake Union, the ship canal, and the Sound all generate them. SFD's fireboats are based at Station 5 on the central waterfront and Station 3 at Fishermen's Terminal. Technical rescues — confined space, high-angle, trench — go to the Rescue 1 company at Station 14 in SoDo. Elevator rescues are surprisingly common — about 2,100 "Rescue Elevator" dispatches in the twelve months ending September 2026 — and they typically draw a single company.
Hazmat
Hazardous materials calls range from a small spilled chemical container to a tank-truck rollover. Seattle's hazmat program operates out of Station 10 in the International District, home of the Hazmat 1 unit. A hazmat dispatch usually includes one engine company for initial isolation and the hazmat team for assessment. Large hazmat incidents — a downtown chlorine leak, for example — would escalate to involve regional partners and Washington State Department of Ecology.
Apparatus, in plain English
- Engine company — a pumper truck. Carries water, hose, basic medical equipment, and a four-person crew. The workhorse of the department. Numbered by station, up to E41.
- Ladder company — a ladder truck (Aerial). Carries forcible entry tools, ventilation equipment, and a 100-foot aerial ladder. Three- or four-person crew. Numbered L1 through L13.
- Aid unit — a non-paramedic ambulance, two-person BLS crew. Numbered by station (for example A2, A10, A25).
- Medic unit — a paramedic ambulance, two-person ALS crew. Eight of them: M1, M10, M17, M18, M26, M28, M31, M32.
- Battalion chief — the on-scene incident commander for major events. Operates from a marked SUV.
- Air unit — carries replacement SCBA (self-contained breathing apparatus) bottles for working fires.
- Rehab unit — climate-controlled support for firefighters working long incidents.
- Hazmat unit, Decon unit, Marine units, Foam unit — specialty equipment dispatched only when the call type warrants.
How to read what you see
Putting it together: when you see a pin on the Seattle Breaking map labeled "Aid Response," that is usually one aid unit responding to a single-patient medical call. When you see "Fire in Building," companies from several stations are converging and traffic on adjacent streets is likely to slow down for a while. When you see "Auto Fire Alarm," that is most likely a non-emergency and the units will usually be back in service quickly.
The grammar of the dispatch type is a remarkably efficient summary once you know how to read it. The data on this site is faithful to it, but you do have to bring the vocabulary yourself.