Fire and EMS Radio Explained — Alarms, Box Assignments, and Medical Traffic

Updated July 23, 2026 · 6 min read

As law enforcement encrypts, fire and EMS have become the most useful channels on most scanners. They are also, once you learn the structure, easier to follow — fire dispatch is highly formalised and describes what is happening far more explicitly than police traffic.

Why fire and EMS stayed open

Fire services depend on mutual aid. A large incident pulls apparatus from neighbouring departments who need to hear the same channel on arrival, and encryption breaks that coordination. EMS has the same problem plus hospital communication.

The result is that in most of the country you can follow a structure fire, a serious accident, or a hazmat response in detail even where police traffic has gone dark.

Alarm levels

The single most useful concept. Alarm level tells you the scale of the response:

• Still alarm / single company — one engine. Smoke detector, smell of smoke, minor call.
• Full assignment / first alarm — the standard structure-fire response: typically three engines, a ladder, a rescue, and a chief.
• Second alarm — the first alarm was not enough. Roughly doubles the apparatus.
• Third alarm and beyond — a major incident. Each level adds another full complement.

When you hear a second alarm struck, something significant is happening. Departments also have specialty escalations: a working fire dispatch adds resources once crews confirm an actual fire, and all hands means every unit on scene is committed.

Box assignments

A box is a predetermined list of which units respond to which location for which call type. The term survives from street-corner fire alarm boxes.

When dispatch strikes "Box 4132", every unit on that box list knows to respond without being named individually. It is why fire dispatch can sound cryptic and then produce eight units.

Apparatus designations

Fairly consistent nationally:

Numbering usually encodes the station: Engine 12 works out of Station 12.

Incident command

On anything beyond a routine call you will hear command established: "Engine 7 on scene, two-storey residential, smoke showing, Engine 7 has Command." From then on, traffic is addressed to Command rather than to individual units.

Useful phrases:

• "Smoke showing" / "fire showing" — visible from outside; this is going to be a working fire
• "Nothing showing" — nothing visible on arrival; often ends quickly
• "Making entry" — crews going inside
• "Water on the fire" — attack has begun
• "Primary search complete" — first sweep for occupants done; "all clear" means nobody found
• "Under control" — no longer spreading
• "PAR" — Personnel Accountability Report, a roll call of everyone on scene
• "Mayday" — a firefighter is in distress. Everything else stops.

EMS traffic

EMS is more constrained because of patient privacy. Dispatch is usually open; the clinical conversation between a medic and a hospital often happens on a separate channel, by phone, or encrypted.

What you will typically hear:

• Dispatch with a call type and a location
• Units marking en route, on scene, transporting
• A destination hospital and sometimes a priority level
• Requests for additional resources — a second ambulance, an engine for lifting assistance, a helicopter

You will occasionally hear a brief patient report. Treat it with the discretion you would want applied to your own family. Most feed operators mute or avoid these channels precisely because of this.

Priority and response codes

The same Code 1/2/3 structure used by police applies:

• Code 1 — routine, no lights or siren
• Code 2 — expedite
• Code 3 — lights and siren

A transport running Code 3 to hospital indicates a serious patient. Most transports are not.

Why it is worth following

Fire and EMS dispatch describes what is actually happening — the building, the vehicles, the conditions, the resources committed. For anyone trying to understand an event in their neighbourhood, it is frequently more informative than the police channel would have been, and it is still there.

For the underlying radio technology, see what is a trunked radio system. For police-side shorthand, see police radio codes explained.