Coverage on the third floor tells you nothing about coverage under the first one. A firefighter who has been talking to command all morning falls through a weakened floor into a basement, and the portable that worked upstairs now has to reach a repeater site miles away through a floor assembly, a foundation wall, and the earth banked against it. That is a geometry problem rather than a hardware problem, and the answer is a radio to radio channel that somebody near the hole is already listening to. This piece covers the mechanism, the tradeoffs, and the relay doctrine that has to exist before the tones drop.

The moment the system stops being the plan

The scenario that makes this argument is ordinary. A crew works a residential fire, the trunked system covers the structure well, portable audio into dispatch is clean from the first and second floors, and nobody has any reason to think about radio at all. Then a floor assembly that has been burning from underneath lets go, and one firefighter is below grade in a space the building had been shielding from view and from RF the whole time.

The radio has not changed in that instant, but the path has, because every element that made the wide area system work, meaning the elevated antenna, the distance, and the arrival angle down onto the roof and in through the windows, now works against the person who needs it most while the portable transmits from the bottom of a concrete box with dirt on three sides toward a receiver on a tower across the county.

The general case for a simplex fireground channel alongside a P25 system is covered elsewhere on this site. What I want here is narrower: the below grade mayday, and the relay path that has to be assigned in advance because it will not be invented at 0400 by people who are already busy.

What simplex actually is

Simplex means the radios talk directly to each other on a single frequency with no infrastructure in the path: no repeater, no site, no controller, no backhaul, no console. On a trunked portable the same idea usually appears as talkaround or direct mode, which takes the radio off the system entirely and puts it on a conventional channel that other portables hear only if they are on it too. It can be analog or digital depending on the fleet, and programming is outside the scope of this piece.

The whole benefit is the shortness of the path. A firefighter in a basement and a company officer at the top of the basement stairs are perhaps twenty or thirty feet apart with one floor assembly between them, so the signal has to survive one floor rather than miles of terrain plus a building shell plus grade. That is why the same portable that cannot raise dispatch from the basement often talks to the crew above it without difficulty.

Why below grade breaks the path

Radio energy into a basement has to get through the building above it, then the floor system, and often soil packed against a foundation wall. Poured concrete with reinforcing steel behaves partly as a shield, soil is worse than concrete, and the openings that leak signal into a structure are almost all above grade, so the paths that carried the signal upstairs do not extend downward. Published loss figures for below grade spaces vary enormously with construction and I will not invent one, but the direction is not in dispute.

Coverage is also not symmetric, and that fools people. A tower site transmits high power into an antenna with gain at height, while a portable transmits a fraction of that from an antenna pressed against a firefighter’s chest, often in water. The downlink survives when the uplink does not, so the firefighter in the hole hears the incident commander perfectly, reads that as a working radio, and does not know that nothing he says is arriving. Crews who have never had this explained will read silence as being ignored.

Digital adds a wrinkle. A signal with forward error correction holds usable audio down to a threshold and then fails over a very short distance, so crews get less warning that they are near the edge than analog noise would give them. Garbled, chopped, or missing, the result is the same: the other side does not have the message and may not know one was sent.

What the 2026 record shows so far

This year has produced several incidents of this type, and I want to be careful about what each one does and does not establish. The most substantial document is the NIOSH Fire Fighter Fatality Investigation and Prevention Program report numbered F2026-01, covering four career firefighters injured in a floor collapse at an abandoned residential structure fire in Kansas and posted in mid April 2026. Read that report through the NIOSH program page rather than any summary of it, including mine.

Two details in the published narrative bear on this topic. The report describes three firefighters falling into the basement when the floor partially collapsed, and an officer who attempted to declare a mayday whose message was unreadable and went unheard, which delayed activation of the rapid intervention team. Recommendations attached to that report include using a personnel accountability system that identifies the location and function of all operating personnel, and ensuring officers and firefighters are trained in mayday operations. I am reporting the published narrative rather than diagnosing the incident.

The news record for 2026 shows the same event shape repeatedly. Firefighter Close Calls reported that on New Year’s Day 2026 at about 11:05 p.m. a mayday was transmitted at a North Patchogue, New York, residential fire when a firefighter fell from the first floor into the basement, and that the member was removed and transported in stable condition. FireRescue1 reported on 26 March 2026 that a Livonia, Michigan, firefighter fell into the basement of a vacant house under renovation the previous morning and was removed without reported serious injury. Those accounts are preliminary and establish nothing about which channel was in use or how it performed, and I raise them only to show the scenario is current rather than hypothetical.

What you give up when you leave the system

Moving interior crews to a simplex channel is a real trade and the losses should be stated plainly. Units not at the scene hear nothing. The telecommunicator who would otherwise catch a mayday the incident commander missed is out of the loop. Console recording goes away, so the interior traffic your after action review most needs is the traffic that does not exist in the logger. The emergency button behavior you are used to changes too, because an alarm pressed off the system does not light up a console with a radio identifier and a talkgroup.

You also lose infrastructure advantages nobody thinks about until they are gone. Receiver voting and multiple receive sites give a weak portable several chances to be heard, and simplex gives it one. Trunking arbitrates access so two people keying at once do not cover each other, while on simplex a doubled transmission is lost and the closest, loudest radio wins, which is not always the one with the most important message.

The middle options deserve honest treatment rather than enthusiasm. In building amplification and distributed antenna systems fix coverage where they are installed and inspected, which in most districts means a minority of buildings and rarely the house where a floor collapses. Vehicle mounted repeaters extend a portable’s reach back to the system and they help, but the apparatus has to be positioned usefully and the uplink still has to make it.

Assigning the channel and naming who listens

The doctrine is not complicated, but each piece has to be written down. One channel is designated for interior operations, everyone entering the hazard zone is on it, and the switch happens at a defined trigger that is the same on every incident, at assignment or at the door rather than at each firefighter’s discretion. A hazard zone where half the crews are on the talkgroup and half are on simplex is worse than either choice made consistently, and a mayday sent on a channel nobody monitors is not a partial success.

Somebody has to own listening. An incident commander at the command post is often too far away and too shielded to hear a simplex transmission from a basement, and is busy anyway. The listening job belongs to a named position with a radio dedicated to that channel, whether that is the interior division supervisor, the rapid intervention officer at the entry point, the safety officer, or a command aide. Name the position rather than the person, and make sure it exists at the staffing you actually put on the street at 0300.

Scanning is not monitoring and one radio is not two radios. A portable scanning between the interior channel and the dispatch talkgroup is busy on one when the other matters, so whoever is expected to hear a mayday on simplex and relay it onto the system needs two radios or a partner. That is a small staffing decision made in advance, and it is the difference between a plan and a diagram.

The relay path has to exist before the fire

A mayday on a simplex channel travels to the incident commander through a human being, and that relay is the part most departments describe in general terms and never rehearse. Write it as a sequence with named positions: who hears it, who acknowledges it on the interior channel so the firefighter knows he was heard, who transmits it to command, and who makes sure dispatch is told, since dispatch is no longer hearing the hazard zone directly and still owns the clock, the resource requests, and the record.

The relay needs to be positioned rather than merely appointed. A rapid intervention officer at the front door of a single family house is inside the simplex bubble, and the same officer at a command post across a parking lot may not be, particularly for a transmission coming out of a basement. In a larger building the relay may need to be at the stairwell landing on the fire floor, and in a high rise the geometry belongs in your standpipe operations plan. What does not change is that somebody in radio range of the trouble has to be listening for it.

Improvising this during the incident does not work, and the reason is not carelessness. A mayday produces a burst of simultaneous demands, including accountability, air, a rescue assignment, and a command decision about whether the strategy still holds, and any task that was not pre-assigned competes for attention at the moment attention is scarcest. Decide who relays while it is boring, in writing, in the document the crews already use.

A channel nobody has practiced on is not a plan

Changing channels under stress is a motor skill performed with a gloved hand, in zero visibility, on a radio worn under a coat where the operator cannot see the display. Treating that as equivalent to changing channels on the apparatus floor in daylight is how a department ends up with a plan nobody executes, and if the interior channel lives in a different zone on your trunked portables, the action may involve menu navigation rather than a knob, which is much harder to do blind.

Drill it the way it will be done, with gloves on, mask on, eyes covered, the radio where it is actually carried, and the crew moving. Have people confirm the change by transmitting and receiving rather than by looking, because looking is the thing they will not be able to do. Keep the channel in the same position across every radio in the fleet, including command staff, mutual aid partners, and the spares in the cache, because consistent placement is what makes the motor skill transferable.

Drill the relay too, and drill the failure. Run the evolution in which the mayday is transmitted and nobody answers, so the rapid intervention crew and the incident commander have practiced acting on absence rather than on information, and run it with the staffing you have at night. Departments that do this find problems in their channel plans within one or two evolutions, and the problems are mundane: a radio that was never programmed, a zone that got reordered, a position that exists on paper and not on the street.

Takeaways

• Coverage verified on upper floors does not predict coverage below grade, because the paths that carry signal into a structure are almost all above grade.
• Simplex is radio to radio with no infrastructure in the path, and its advantage in a basement is the short path rather than any superiority of the equipment.
• Coverage is not symmetric, so a firefighter can hear command clearly while nothing he transmits reaches anyone.
• Leaving the trunked system costs wide area coverage, dispatch monitoring, console recording, receiver voting, and normal emergency button routing.
• NIOSH report F2026-01, posted in mid April 2026, describes firefighters falling into a basement and a mayday attempt that was unreadable and went unheard.
• The 2026 news accounts of firefighters falling into basements are preliminary and establish nothing about which channels were used or how they performed.
• The relay from the interior channel to command must be a named position physically within range of the hazard zone, and it needs two radios or two people.
• Switching channels blind with a gloved hand is a learned skill, so drill it under mask and in the dark, including the evolution where the mayday gets no answer.