MRI Suite Signage: Zone I Through Zone IV

The magnet is always on. Signage is how a building tells people that.

An MRI magnet does not switch off between patients. It is at full field 24 hours a day, and the accidents that happen in MR suites, projectiles, implant interactions, burns, are almost always someone entering a space they did not understand. The American College of Radiology's four-zone model exists to make that space legible, and signage is how the zones become real to the people walking through them.

Shop MRI safety signage

The four zones

Zone I is everywhere the public can go freely: the lobby, the waiting room, the corridor outside. No hazard, no restriction.

Zone II is the interface. Patients are greeted, screened, and interviewed here under supervision. This is where the first screening signage goes, because it is the last place someone with a pacemaker or a steel implant can still be turned around without entering a controlled area.

Zone III is restricted. Only screened MR personnel and screened patients under direct supervision. Access must be physically controlled, meaning a locked door, not a sign alone. The control room and equipment areas are here.

Zone IV is the scanner room itself, inside Zone III. The ACR requires it to be clearly marked as potentially hazardous, typically with a lighted sign or red light at the door indicating the magnet is on, and it is the only zone where the projectile effect is immediate.

What goes on the signs

• At the Zone II to III boundary: screening required, do not enter unscreened, no unauthorized personnel
• At the Zone IV door: strong magnetic field, the magnet is always on, no ferrous metal objects, no pacemakers or implants without clearance
• Inside Zone IV: radiofrequency burn hazard notices near the bore, and emergency stop identification that distinguishes an emergency stop from a quench
• At the quench vent termination: outside the building, at roof or exterior wall, warning of cryogen discharge and oxygen displacement. This one gets missed because it is outside the imaging department, in a place roofers and HVAC contractors work

Ferromagnetic detection

The ACR recommends ferromagnetic detection systems at the Zone III to Zone IV boundary. A detector is only useful if people know why they are being screened, which is where posted signage supports the workflow rather than replacing it.

Why aluminum, specifically

This is the one category where the substrate is a safety issue in itself. A steel sign, or a sign with a steel frame or steel mounting hardware, is a projectile in Zone IV. Aluminum is non-ferromagnetic. It does not become a missile near the bore. That is not a durability argument, it is the reason you cannot use most of what other sign companies sell in an MR suite.

Browse MRI safety signs

Source: ACR Manual on MR Safety, American College of Radiology. The four-zone model and Zone IV marking requirements are drawn from that document. Facility layout, door control, and signage placement should be reviewed by your MR safety officer.