MRI-safe fire extinguishers are designed to protect these expensive and life-saving machines from damage in the event of a fire. High specification CO2 fire extinguishers and water mist extinguishers are designed with non-magnetic components to be able to operate in the vicinity of a magnetic resonance imaging (MRI) machine.
How MRI-Safe Fire Extinguishers Work
MRI-safe fire extinguishers are essentially the same as normal extinguishers on the inside. However, MRI-safe fire extinguisher cylinders must be non-magnetic, as the magnetic field of an MRI machine is strong enough to attract a normal fire extinguisher with bone-crushing force.
It is not often realised but the magnetic potency of an MRI machine stays for a long time after it is turned off. This prevents fire-fighters from entering with something as simple as a metal belt buckle. There have been incidents of people being “sucked” into an MRI with tragic results.
The same rule applies to any machinery with a strong magnetic field, such as nuclear magnetic resonance spectrometers (NMR’s). Non-magnetic fire extinguishers should also be used in health centres, clinics, and any premises where magnetic interference might affect the performance or operation of sensitive equipment.
Non-magnetic fire extinguishers are made with a non-magnetic stainless steel or aluminium shell, and non-magnetic fittings such as valves, nozzles and pins.
Specially manufacturerd 2kg CO2 fire extinguishers are the most popular non-magnetic type in the UK, since they can be used to extinguish fires in, on or around electrical equipment, are clean to operate and do not leave any residue after use. The non magnetic fire extinguisher is available online from Fire Protection Online and is made by Chubb Fire (and also sold under their sister company name of Thomas Glover).
Water Mist Fire Extinguishers
Amerex Corporation of the USA developed their water mist extinguisher for use in clean rooms, telecoms areas and health care facilities. Using distilled water instead of tap water, it has a specially-developed misting nozzle that atomizes the water making it non-conductive.
These are available in 1.75 gallon and 2.5 gallon size and as a 9 litre size in the UK (model 272) BAFE approved to BS EN3. They have UL approval in the USA.
As you can imagine, high specification non-magnetic fire extinguishers do not come cheap, retailing at a premium to the standard models. But, they can be found online at much lower prices.
The MRI had to be quenched because much of the equipment that fire fighters carry — axes, picks, oxygen tanks and more — contains ferrous material and would have been sucked into the unit by its magnetic force. Their equipment, and anything metal, could have become MRI-seeking missiles, as other firefighters have learned. According to Gilk, a firefighter in Stockton, Calif., last year lost his ax to the pull of an the MRI while he was ventilating the roof a building.