The plain language radio protocol under NIMS requires emergency responders to communicate in ordinary English, not agency codes or acronyms, whenever an incident involves more than one agency, jurisdiction, or discipline. The rule has been tied to federal preparedness grant eligibility since fiscal year 2006, and because multi-agency response is the norm at any serious incident, it reaches nearly every responder in the country.
When Plain Language Is Required
A common misreading is that NIMS bans 10-codes outright. It does not. FEMA’s 2006 implementation alert states plainly that “the use of 10-codes in daily operations will not result in the loss of federal preparedness funds.”1Federal Emergency Management Agency (FEMA). NIMS Alert – NIMS and Use of Plain Language A police department can keep its internal codes for routine patrol on its own channels.
The requirement kicks in the moment an incident crosses organizational lines. When a fire department, an EMS agency, and a county sheriff’s office all work the same scene, every transmission between those organizations must use plain language. That covers oral communication, written messages, and any radio traffic on shared frequencies. Personnel should also avoid acronyms or jargon unique to their own agency during these events.2Federal Emergency Management Agency (FEMA). National Incident Management System (NIMS)
The 2017 NIMS doctrine defines plain language as “a communication style that avoids or limits the use of codes, abbreviations, and jargon, as appropriate, during incidents involving more than a single agency.”2Federal Emergency Management Agency (FEMA). National Incident Management System (NIMS)
What Plain Language Sounds Like on the Air
Clear text means using standard English words that any listener can understand without a decoder ring. In practice, that means replacing 10-4 with “copy” or “received,” saying “en route” instead of a numeric status code, and describing conditions in ordinary words rather than signal numbers.
Common Terminology for Roles and Facilities
NIMS standardizes more than radio chatter. It sets common names for organizational roles, facilities, and resources so everyone at an incident works from the same vocabulary. The person running the scene is the Incident Commander. The place that person works from is the Incident Command Post. Staging areas, base camps, and divisions each have fixed definitions that apply regardless of which agency staffs them. Position titles like Section Chief, Branch Director, Division Supervisor, and Unit Leader describe specific levels in the ICS structure, and responders use those exact titles when addressing someone in that role.
Resource Typing and Unit Identification
NIMS uses a national system for categorizing equipment and personnel by capability. Resource typing defines and categorizes resources by what they can do, so that when an Incident Commander requests a specific type, the dispatching agency sends something that meets the need.3Federal Emergency Management Agency (FEMA). Resource Typing – National Resource Hub A Type 1 engine and a Type 6 engine have very different pump capacities, tank sizes, and crew requirements. Using the national type designation instead of a local nickname ensures the right resource shows up. On the radio, units identify themselves by their full functional name, such as “Engine 5,” “Ambulance 12,” or “Hazmat 1,” not by a badge number or station shorthand that outside agencies wouldn’t recognize.
The Phonetic Alphabet
When responders need to spell out names, addresses, or license plates, the standard is the NATO phonetic alphabet: Alpha, Bravo, Charlie, and so on. It eliminates confusion between similar-sounding letters like B and D or M and N, which can be nearly impossible to distinguish through static. A license plate reading “BDM-4192” becomes “Bravo Delta Mike four one nine two.” The alphabet is consistent across law enforcement, fire, EMS, and military agencies.
Radio Call Format and Transmission Discipline
Radio traffic under ICS follows a recipient-first format. The caller names who they are trying to reach, then identifies themselves. A medic contacting the Incident Commander says: “Command, Medic 4.” That tells everyone on the frequency who needs to listen and who is talking. Wildland fire training describes this as the “to-from” format and recommends also identifying which channel you are using so the recipient knows where to respond.
Every transmission should be as short as possible while still being complete. Wait for the channel to clear before keying your mic. Pause briefly after pressing the transmit button so the first word does not get clipped. Release the button promptly when finished. When you receive critical information, such as an assignment change or a hazard warning, repeat the key details back to the sender. That confirmation loop catches errors before they turn into problems on the fireground.
Priority Traffic and MAYDAY
Three tiers of priority traffic are widely used across emergency services, escalating in severity:
- Urgent. Information that is not an immediate threat to life but needs quick attention: a sudden change in conditions, a resource request that cannot wait, or a developing risk to personnel.
- Emergency traffic. An immediately dangerous condition affecting people on scene, such as imminent structural collapse, flashover, or a downed power line. When someone transmits “emergency traffic,” all other users on that channel go silent until the emergency communication is complete.
- MAYDAY. Reserved for a responder in personal danger who needs rescue, whether trapped, lost, injured, or running out of air. A MAYDAY overrides everything else on the frequency.
When declaring a MAYDAY, the standard practice is to transmit “MAYDAY, MAYDAY, MAYDAY” and then provide your location, unit designation, the names or numbers of personnel in trouble, your assignment at the time, the resources you need, and your situation (low air, trapped, pinned). Some agencies teach the mnemonic LUNARS to cover those elements. The order matters less than getting all the information out. Once a MAYDAY is resolved, the person who called it transmits the cancellation three times and waits for confirmation from command.
Tactical Exceptions
The 2017 NIMS doctrine acknowledges that plain language is not always appropriate. It notes that “tactical language is occasionally warranted due to the nature of the incident,” using an ongoing terrorist event as an example.2Federal Emergency Management Agency (FEMA). National Incident Management System (NIMS) Law enforcement tactical teams and undercover operations sometimes need encrypted or coded communication to protect officer safety and operational security.
When an incident requires that kind of exception, the guidance calls for incorporating specific rules about encryption and tactical language into the incident-specific communications plan. The exception does not give any agency a blanket pass to revert to 10-codes. It is narrow, it applies to genuinely sensitive tactical situations, and it has to be documented in the plan so other agencies on scene understand why certain traffic is encrypted and how information routes to and from those teams.
The Incident Radio Communications Plan (ICS 205)
At any incident large enough to require a formal Incident Action Plan, the Communications Unit Leader prepares ICS Form 205, the Incident Radio Communications Plan. This single-page document lists every radio frequency and talkgroup assignment for the operational period, organized by function: command, tactical, ground-to-air, support, and dispatch channels.4FEMA Training. ICS Form 205 – Incident Radio Communications Plan Each entry includes receive and transmit frequencies, tone codes, whether the channel runs analog or digital, and which branch, division, or group it serves.
The form is distributed to everyone who receives the Incident Objectives (ICS Form 202), including the Incident Communications Center.5National Public Safety Telecommunications Council (NPSTC). Instructions for Completing Incident Radio Communications Plan (ICS Form 205) Frequency assignments from the 205 also flow into the Assignment Lists (ICS Form 204) so individual teams know which channel to monitor. Standardized channel naming conventions, developed by organizations like NPSTC and APCO International, mean that when an ICS 205 lists a national interoperability channel, every agency’s radios should already have it programmed under the same name.
Grant Compliance Consequences
The financial teeth behind the requirement come from Homeland Security Presidential Directive 5, which made NIMS adoption a condition for federal preparedness grants.6Department of Homeland Security. Homeland Security Presidential Directive 5 – Management of Domestic Incidents That flows through to a range of FEMA grant programs, including the Homeland Security Grant Program (which covers the Urban Area Security Initiative and Operation Stonegarden), the Emergency Management Performance Grant, the Transit Security Grant Program, and the Port Security Grant Program.7Federal Emergency Management Agency (FEMA). Preparedness Grants Manual Agencies that cannot demonstrate NIMS compliance, including plain language use during multi-agency events, risk losing eligibility for those funds.
Training and Adoption
Transitioning to plain language starts with updating standard operating procedures to explicitly replace coded communication with clear text for multi-agency operations. That policy document becomes the baseline supervisors enforce and auditors review.
FEMA’s Emergency Management Institute offers online courses that cover NIMS principles, including communication standards. The foundational courses most agencies require their personnel to complete include:
- IS-100: Introduction to the Incident Command System
- IS-200: ICS for Single Resources and Initial Action Incidents
- IS-700: An Introduction to the National Incident Management System
- IS-800: National Response Framework, An Introduction
IS-700 specifically addresses communication characteristics and standards under NIMS, including the rationale for plain language.8FEMA.gov. IS-700.B – An Introduction to the National Incident Management System The courses are free through FEMA’s independent study program, and completion certificates serve as documentation during compliance audits.9FEMA.gov. NIMS Implementation and Training
Classroom instruction only goes so far. The real transition happens during tabletop exercises, functional drills, and full-scale multi-agency exercises where responders practice speaking in clear text under realistic pressure. Recruits pick it up quickly because they have no old habits to break. Veterans who have used 10-codes for twenty years are the ones who revert under stress, and that is where supervisory monitoring of radio traffic matters most. Many agencies record transmissions and conduct periodic reviews, giving corrective feedback to personnel who slip back into coded language.