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," "Aid-MVI," "Auto Fire Alarm — Commercial," "Investigate Out of Service," "MVA Freeway Block." There are roughly forty of these type strings in active use, 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 aid unit — a two-firefighter ambulance staffed by BLS-certified personnel — 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 see an AID Response on the feed with multiple units attached (an engine company plus an aid unit, for instance), that usually means the closest aid unit was unavailable and an engine was sent as the first responder to begin assessment while the aid unit traveled from a farther station.
Medic Response
"Medic Response" is the paramedic-level upgrade. It dispatches one of Seattle's seven 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.
Aid-MVI
"Aid-MVI" — sometimes written "AID — MVI" — is a medical aid call dispatched to a motor-vehicle incident. The presence of "MVI" in the type string tells you that the call originated from a collision report. Response plans for Aid-MVI typically 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 — Residential / Commercial / High-Rise
"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 one engine, sometimes a ladder if the building is multi-story. Often clears within five to ten minutes once the engine company confirms no fire.
- Commercial alarm — usually one or two engines plus a ladder truck, occasionally with a battalion chief on scene if the building is large or sensitive.
- High-rise alarm — three to four engines, two ladders, a battalion chief, and an Air unit (which carries replacement SCBA bottles). High-rise response is heavily weighted because vertical evacuation and standpipe operations are resource-intensive.
Structure Fire
"Structure Fire" is what it sounds like — a confirmed or suspected fire inside a building. A first-alarm structure fire response in Seattle dispatches three engine companies, two ladder companies, a medic unit, an aid unit, an Air unit, a battalion chief, and a deputy chief. That is roughly 25 firefighters and 9 pieces of apparatus on the initial alarm. A working fire (one that is actively burning and requires interior firefighting) can escalate to a second or third alarm, doubling or tripling the assignment.
If you see a Structure Fire 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 triggers additional automatic dispatches: a second alarm assignment, the Rehab unit, additional Medic units, and the Safety Officer. If you see "Working Fire" appear on the feed, the underlying incident has escalated significantly.
MVA Freeway Block / MVA — No Injuries / MVA — With Injuries
"MVA" stands for motor-vehicle accident. The qualifiers tell you the freeway dimension and whether injuries were reported. MVA Freeway Block always dispatches 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. MVA — With Injuries dispatches an aid unit plus engine. MVA — No Injuries often only dispatches an engine for hazard control (fuel spills, debris).
Investigate Out of Service / Investigate Smoke / Investigate Odor
The "Investigate" family of types is what SFD uses when the call doesn't fit a higher category but warrants a unit checking it out. "Investigate Smoke" is a smoke report with no visible fire. "Investigate Odor" is a gas, smoke, or chemical smell. "Investigate Out of Service" is typically a damaged hydrant, a triggered fire suppression system that isn't fully clear, or a similar infrastructure concern. Response is usually one engine, occasionally a hazmat unit for odor calls.
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 operates a dedicated Marine division with two fireboats based at Stations 5 (downtown waterfront) and 14 (south Lake Washington). Technical rescues — confined space, high-angle, trench — go to the Rescue 1 company. Elevator rescues are surprisingly common in a city with many older buildings; they typically dispatch one engine and clear within twenty minutes.
Hazmat
Hazardous materials calls range from a small spilled chemical container to a tank-truck rollover. Seattle's hazmat program operates out of Station 2 (downtown) with the Hazmat 1 unit, plus a decontamination 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 E1 through E39.
- 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 L11.
- Aid unit — a non-paramedic ambulance, two-person BLS crew. Numbered A1 through A30+.
- Medic unit — a paramedic ambulance, two-person ALS crew. Seven of them: M1, M10, 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 one aid unit responding to a single-patient medical call, probably arriving within four to six minutes. When you see "Structure Fire," roughly 25 firefighters are converging from three or four stations and traffic on adjacent streets is about to slow down for an hour. When you see "Auto Fire Alarm — Commercial," that is almost certainly a non-emergency and the units will be back in service within fifteen minutes.
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.