Magnesium is one of a few metals that can catch fire. A highly reactive silvery looking metal which burns with a fierce light and generates an appreciable amount of heat. So, if you find yourself in a situation when magnesium has caught fire, what should you do? Here’s everything you need to know.
You can put out a magnesium fire, if you are trained and confident doing so, by using a Class D fire extinguisher that is specifically designed to extinguish flammable metal fires.
Let’s take a look at flammable metal fires, what you need to know and how to handle them. Keep reading.
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Also read: Does Metal Burn In A Fire? Examined
Why Does Magnesium Burn So Easily?
Magnesium has a very low ignition point and it is a very reactive element.
Take a look at firefighters at a magnesium car fire:
The reactivity of Magnesium is explained by its atomic structure which makes it easy for the element to accept a pair of electrons (like those provided by Oxygen when it is reduced into ions).
This reaction Mg (Magnesium) + O (Oxygen) = MgO (Magnesium Oxide) is extremely powerful and fast and highly exothermic (releases quite a bit of bright light, which you may remember from high school chemistry lessons).
Strangely, the finished product of Magnesium Oxide is quite useful and can be used in antacids as well as to deliver a mild laxative effect.
However, because the reaction is heavily exothermic (that is it puts out huge amounts of heat). Magnesium fires can spread very quickly to anything around them.
The biggest problem though is that you can’t extinguish a magnesium fire with water, in fact, it’s extremely dangerous to do so.
Also read: Is Aluminum Flammable?
Why You Shouldn’t Use Water?
Water reacts with magnesium.
In fact, it reacts with magnesium at room temperature, though it does so slowly enough that you won’t really notice it unless you allow large amounts of damp magnesium to sit around in an enclosed space, in which case things will eventually turn explosive.
Magnesium reacts with the oxygen molecule in water to form Magnesium Oxide (as in our equation above) and that releases pure hydrogen gas.
If you cast your mind back to school chemistry lessons or the history lesson on the Hindenburg Disaster, then you will know that hydrogen burns very well in the presence of oxygen.
It forms more water, which then rains down on the magnesium fire, and makes more magnesium oxide and hydrogen. Thus, this reaction can quickly become self-sustaining and it’s very likely to help push your magnesium fire all the way through the building you’re trying to save.
So, whatever you do, in the event of a magnesium fire do not use any time of water extinguisher, things will not end well if you do.
Nor should you use a Class B extinguisher (Carbon Dioxide). This gas can also be become a combustive oxidizing agent and make the reaction turn violent.
Here is a look at what happens when you use a water extinguisher on a magnesium fire:
Also read: Is Copper Flammable?
What Class Of Fire Is A Magnesium Fire?
A magnesium fire is a Class D fire and fighting one is not as simple as you might think. In fact, the fire service has often struggled with magnesium fires.
Firehouse magazine recounts that in 1988, a tractor-trailer fire (and ensuing explosion) forced nearly 200 people to evacuate from two local factory compounds. Inside the trailer was magnesium, lots of it. The fire burned so hot (over 2,000 degrees Fahrenheit) that it melted the trailer it was being held in.
Firefighters could not extinguish the blaze and it had to be left to burn out by itself. Yet, the fire department didn’t have an easy time of things – they had to prevent the fire from spreading and spent a whole night cooling down the area around the fire.
Then again in 2011, in North Carolina, a fire crew was called to a vehicle fire. Many vehicles use some magnesium in their construction and as the crew approached the blaze with their hose and let loose with the water – it hit the magnesium element. One firefighter was so badly injured in the resulting explosion that they are no longer able to work for the service.
So, it’s important to realize that magnesium fires are not trivial. That even highly skilled and well-trained professionals can find themselves in a position where they struggle to deal with magnesium fires.
This should be a warning to you too – there is no shame in admitting that you do not feel safe when tackling a magnesium blaze and calling for the fire department.
Also read: Is Sodium Flammable?
How Do You Put Out A Magnesium Fire?
In order to tackle a magnesium fire, you will need a Class D fire extinguisher, which contains MET-L-X Powder. That powder is Sodium Chloride which you may recognize as common table salt.
Why sodium chloride? Well, firstly, it’s cheap which makes it very economical to use in fire extinguishers, but also it requires very, very high temperatures to break the Sodium-Chlorine bonds, and thus, in metal fires such as a magnesium fire, it’s completely unreactive.
- To tackle a fire with this kind of extinguisher, you begin by pulling the pin, then hold the extinguisher whilst ensuring that the nozzle is pointing at the fire.
- You hold the nozzle above the fire (the maximum reach of the nozzle is approximately 6 feet, no more).
- Then you squeeze the discharge lever whilst keeping the body of the extinguisher in a vertical position.
- Then sweep the nozzle back and forth so that it applies a thin layer of powder over the base of the fire.
Once it appears you have control of the fire and it’s not spreading – you can increase the depth of the powder so that it forms a heavy seal over the powder. Do not crack this seal or otherwise interfere with it – let the fire department handle the rest.
You can use the acronym PASS to remember the steps for using a fire extinguisher effectively:
- Pull the pin
- Aim the nozzle
- Squeeze the discharge lever
- Sweep the nozzle back and forth to cover the base of the fire
It takes just under 30 seconds to empty one of these extinguishers – if the blaze isn’t out by then, it’s time to step away and wait for the fire department.
What To Do For Smoke Or Fire?
Whenever you discover fire, the best thing that you can do is to alert others.
You can shout “Fire!” which will help to warn people who are nearby and if you have an alarm system within the building, it is important to trigger that before you do anything else.
You should also call the emergency services (911) and let them know too.
You shouldn’t attempt to try and tackle the blaze yourself until you have done these things as they hugely increase the odds that if something does go wrong, the people around you will be safe.
Then it’s important to realize that you only tackle a fire if you feel confident to do so.
In the case of a magnesium fire, it is very important that you understand what you are dealing with, the risks involved, and why the best decision, when combating a magnesium fire, maybe to leave the job of putting the fire out to the professionals.
When handled incorrectly a magnesium fire can become incredibly dangerous to you and to everyone in the area. It’s always best not to take any chances with this kind of fire. Your life and safety are more important than property.
Conclusion
How do you put out a magnesium fire? Most of the time, you don’t. As you’ve seen, even trained firefighters can struggle to deal with a large-scale magnesium fire. However, as long as the fire is small and has no major risks of spreading, then you can grab a Class D fire extinguisher and if you feel confident to do so, you can extinguish the fire with it.
You should never tackle a fire unless you are completely certain that it is safe to do so. If you are in any doubt, move to a safe place, pull the fire alarm and call 911. There’s no shame in this, that’s why firefighters exist – to protect the public from fires.
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