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Two urban search and rescue markings carrying the same information in incompatible notations.
The international system draws a square beside the entry point and fills its quadrants with the team, the times, the hazards and the number of casualties remaining. The United States system draws a large cross and uses its quadrants for the same purpose, with one stroke made on entering and the second on leaving — so an incomplete cross means a team went in and has not come out. They are used side by side on international deployments, and reading one as the other misreports whether anyone is still inside.
The international system uses a square and the US system a cross, for the same information.
Drawn from the visual attributes recorded for each symbol. Only traits the two records disagree about are listed.
| Trait | INSARAG structure marking | FEMA search marking |
|---|---|---|
| Built from | squares and letter like | crosses and letter like |
| INSARAG structure marking | FEMA search marking | |
|---|---|---|
| Outline | A square. | A diagonal cross. |
| Signals search complete | A diagonal line drawn across the square. | The second stroke of the cross, made on exit. |
| Incomplete mark means | Search in progress. | A team entered and has not come out. |
| Relationship (from Symbolwise's records) | Commonly confused with FEMA search marking — The international system uses a square and the US system a cross, for the same information. | Commonly confused with INSARAG structure marking — The US system uses a cross and the international system a square, for the same information. |
Emergency management marking and triage systems
FEMA, INSARAG and comparable national and international agencies · retrieved 2026-08-27
Cited for the identity and defined meaning of structure markings, triage categories and incident symbology. National systems differ and a record names the system it describes. Not cited for clinical guidance of any kind.
A building's assembly point is a safe place to stand once you are outside. A ship's muster station is a staffed step in a procedure: you are counted against a roll, briefed, and if necessary allocated to a survival craft, which is why it has a letter or a number and appears on your cabin door card. Both are green, both show grouped figures, and both are called an assembly point in ordinary speech — and treating a muster station as somewhere merely to wait is the misunderstanding drills exist to correct.
The becquerel counts nuclear decays — one per second — and says nothing about harm. The sievert weights absorbed energy by the kind of radiation delivering it, and so estimates biological effect. A becquerel of one isotope and a becquerel of another can carry very different risk, which is exactly why exposure limits and medical doses are stated in sieverts and never in becquerels.
Count what is around the centre. Three solid blades radiating from a small disc is ionising radiation; three broken rings overlapping a central circle is biological hazard. They are the same size, the same colours and the same three-fold arrangement, which is why signage catalogues themselves get them wrong — and the responses could not be less alike. One calls for distance, shielding and time; the other for containment, disinfection and a disposal route.
The plain black flag excludes the competitor: their race is over. The black flag with an orange disc reports a mechanical problem that endangers others and sends the driver to the pits to have it fixed, after which they may rejoin. Both are shown with a number board, both are black, and confusing them costs a competitor a race they could have finished.