Guide
MRI Safe Fire Extinguisher Cabinets
What NFPA 99 requires in an MRI room, what MR Safe under ASTM F2503 actually means, and why the Cato Island Chief is the all-plastic answer.
An MRI scanner runs a magnetic field between roughly 1.5 and 7 Tesla and it does not switch off between patients. Anything ferrous that enters the room becomes a projectile. That is why the cabinet on the wall matters as much as the extinguisher inside it.
What the code actually says
Until 2018, guidance for extinguisher selection in MRI rooms, operating rooms, cooking areas and telecommunications rooms was vague. The International Code Council Committee on Healthcare then adopted the NFPA 99 Healthcare Facilities Code, and NFPA 10 section 5.6, "Selection for Specific Locations," now points at it. Both the International Fire Code and the International Building Code reference NFPA 10 for selection, installation and maintenance of portable extinguishers, so the chain ends at NFPA 99 either way.
NFPA 99 Chapter 16, "Features of Fire Protection," applies to both new and existing healthcare facilities, and lets existing non-compliant systems remain in use unless the authority having jurisdiction determines there is a hazard to life.
The MRI clause is short:
16.10.1.1.1 Fire extinguishers and associated hardware rated as MR conditional or MR safe shall be provided in MRI rooms and associated spaces.
Read "associated hardware." A non-magnetic extinguisher hanging in a steel cabinet does not satisfy that sentence.
What MR Safe means
ASTM F2503 is the standard for marking items for safety in the magnetic resonance environment. An item labeled MR Safe poses no known hazard in any MR environment, because it is electrically non-conductive, non-metallic and non-magnetic. MR Conditional is the weaker label: safe under stated conditions, such as below a stated field strength.
Cato's NFPA 99 article states the general case directly: all-plastic cabinets with no magnetic components as defined by ASTM F2503 can be used in MRI rooms with MR safe fire extinguishers.
The Cato Island Chief
The Island Chief is the Cato model built for this. Its submittal states that it is MR Safe labeled, as defined in ASTM F2503, is safe to use in a magnetic resonance imaging environment, and is composed of materials that are electrically non-conductive, non-metallic and non-magnetic. The Cato flyer repeats the same claim. An MR Safe label, part LA-1041, 2 in. x 2 in., is applied to the pull panel.
Construction:
- Tub and trim — injection molded high-impact polystyrene, .110 thickness, UV inhibitors, red or white
- Cover — .030 PETG panel with an oval notch cut out that forms a hand pull
- Hardware — ABS hexagonal lock with two keys, used to remove the trim and panel
- Decals — "FIRE" on the tub sides, "Tampering is a Felony" and MR Safe on the pull panel
There is no break hammer, no stainless break bar and no steel hinge, because there is nothing metal in the cabinet. In an emergency you hook a hand into the notch and pull the panel off.
Sizes and tub interiors:
| Model | Size | Tub I.D. (W x H x D) | Ship weight |
|---|---|---|---|
| 10501-P / 10551-P | 5 lb | 6" x 16-3/4" x 5-3/8" | 3.5 lb |
| 11001-P / 11051-P | 10 lb | 6-3/4" x 20-1/2" x 6" | 4.5 lb |
| 12001-P / 12051-P | 20 lb | 9" x 26" x 8" | 6 lb |
The 20 lb Island Chief appears on Cato's submittal table but is not priced on the current 8C distributor price sheet. Ask us to quote it rather than assuming stock.
Which extinguisher goes inside
The cabinet's MR Safe label does nothing for a ferrous cylinder. Cato's Island Chief submittal names the non-magnetic units it was laid out around: the JL Industries Sentinel 5-5BNM carbon dioxide unit and the JL Industries Nebula 270-272 water mist units. Both are agent types NFPA 99 favors here.
The reasoning, from Cato's own article: two types of non-magnetic extinguisher have been developed, carbon dioxide and water mist. Neither leaves a residue, both are non-conductive, and both are effective on sensitive electronic equipment. Water mist works on Class A and C fires and isolates the user from electrical shock because the water leaves as microdroplets. Carbon dioxide works on Class B and C by displacing oxygen and removing heat — though CO2 should not be used on human tissue, which matters in a clinical space.
ABC dry chemical is the agent to keep out. It could damage or destroy the scanner; a non-magnetic ABC unit belongs in an adjoining room, not in the magnet room.
Always confirm the MR rating and the tested field strength with the extinguisher manufacturer against your own scanner. A nameplate that reads "tested up to 3 Tesla" is not adequate for a 7 Tesla research magnet.
The rest of the healthcare suite
While you are specifying, NFPA 99 Chapter 16 covers three other spaces:
- Operating rooms — 16.10.1.4: clean agent or water mist. Halotron I clean agents are not recommended for operating rooms; exposure may cause central nervous system and cardiac effects.
- Telecommunications entrance facilities and equipment rooms — 16.10.1.5: clean agent type, which leaves no residue and is electrically non-conductive.
- Cooking areas — 16.10.1.2: Class K, for combustible cooking media.
One more clause worth knowing
Cabinets housing extinguishers generally may not be locked. IFC 9.05.7.2 and NFPA 10 6.1.3.7 allow exceptions: a frangible glass or transparent panel that is easily broken, approved locking options, Group I-3 occupancies, and mental health areas in Group I-2 occupancies where staff hold keys. The Island Chief's pull panel is a tool-free opening, which is the simplest way to stay on the right side of that.
This is reference material, not a code ruling. Consult the actual code publications and your authority having jurisdiction.