Iron is the most common element on Earth by mass and it’s the metal that we’re most familiar with, it’s everywhere from the utensils we eat with to the fencing that protects our properties, to the cars that we drive. But should we be so careless about the use of iron? Are we potentially introducing a fire hazard into our lives and if so, what should we do about that?
Iron is not generally considered to be flammable. It has a very high ignition temperature, which makes it difficult to ignite. However, in smaller forms, like iron shaving/filings or steel wool, it can catch fire much more easily, due to the greater surface area.
Let’s take a closer look at these differences. This is what you need to know about iron and fire.
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Also read: What Makes Something Flammable?
What Is Iron?
Iron (chemical symbol Fe) is the most common element on the planet by mass (it accounts for 32.1% of the earth’s total mass).
It is also, the fourth most common element in the Earth’s crust though it is rarely found as pure iron but, instead, in ores.
Any pure iron in the Earth’s crust is likely to be of extra-terrestrial origin and have been deposited by a meteor strike!
Extracting iron from its ores is not an easy process and it requires intense heat of above 2,730 degrees Fahrenheit (that’s 1,500 degrees Celsius) which is a lot more heat than that required to smelt copper.
This is why the “Iron Age” didn’t start until around 2,000-1,200 B.C. as human beings weren’t capable of creating fires of such intensity until then.
Iron and steel (which is an iron-carbon alloy) are the most commonly produced metals in the world even today thanks to their excellent mechanical and chemical properties and relatively low cost.
Iron and steel have a silvery-gray appearance in their untarnished form.
What Is It Used For?
Iron is very important in the human body and each of us contains about 4 grams of iron – mostly in the two oxygen transport chemicals, hemoglobin, and myoglobin.
They allow the blood and muscles to store and use oxygen readily.
You will find iron in most plants and animals carrying out similar roles.
It is used widely in many industries as a structural material (ships, airplanes, railways, automobiles, buildings, etc. all rely on iron) and, in most cases, it is found as steel which is harder than pure iron.
Iron compounds are used in a wide variety of industrial roles included ammonia production, carbon conversion, dyes and pigments, etching circuit boards, animal feed additives, animal medicines, treating cement, and much more.
Is Iron Flammable?
Under normal circumstances, iron is neither flammable nor combustible.
However, it is worth noting that there are some types of iron and iron compounds that are easy to burn, which we’ll touch on in a few minutes.
It’s also important to recognize that if iron or steel is heated in the presence of pure oxygen (as it often is in industrial processes) this changes the flammability of iron, it won’t “burn” per se, but it will become hot enough that it melts a little and sprays sparks all over the place.
Why Is Iron Not Combustible?
Iron only burns at very high temperatures. In fact, it needs a temperature of over 1500 degrees Celsius or 2,730 degrees Fahrenheit for it to burn.
These are much higher temperatures than you are likely to encounter in everyday life and as such iron does not meet the definition of a combustible substance which is a solid that burns easily at relatively low temperatures.
Is Steel Non-Flammable?
Steel, rather like iron, is neither flammable nor combustible.
Steel is created by adding carbon to iron and this process does change the properties of the iron.
As you may know, it’s possible to create “stainless” steel which does not oxidize (rust) over time.
Steel is also harder than iron and is a better material to use when strength is critical.
However, that doesn’t extend to the flammability of steel and steel is no more combustible or flammable than iron and needs extremely high temperatures in order to burn.
Can Fire Burn Steel?
In most building fires the temperature is not hot enough for the iron or steel to ignite and often, the metal frames are all that’s left behind.
However, it is possible, particularly in some kinds of industrial fire, for other elements to be present in a fire and allow for the combustion of iron and steel but this would be a rare event.
Is Steel Wool Flammable?
Steel wool is made of iron and carbon and it will burn very easily, in fact, it burns so easily that many a chemistry teacher has shown their class what happens when you put steel wool in a Bunsen burner flame.
It ignites immediately. Check it out:
So, why is this flammable when steel and iron are not?
It is more readily combustible than iron and that’s because there’s a much greater amount of surface area to the volume of the iron than there is in a solid lump of iron.
This allows for far more heat to be taken into the material than it would absorb under usual circumstances and starts the ignition reaction at a lower temperature.
Also read: Is Steel Wool Flammable?
What About Iron Filings?
Iron filings may be combustible (like steel wool – they are not flammable) and it really depends on the size of the filing.
The smaller and more dust like the filings, the more of a fire risk that they become and for the same reasons as the steel wool (more surface area to volume).
It is also worth noting that iron filings may also be an explosion hazard as if they begin to burn, they will produce enough heat to burn more iron filings, if the iron filings are spread out through the air when they ignite – they will explode.
Are Iron Nails Flammable?
Iron nails are not flammable nor are they particularly combustible.
For all intents and purposes, an iron nail is a solid block of iron and has the same chemistry as a solid block of iron does.
What Happens When Iron Is On Fire?
When iron burns it forms “iron oxide” which is a substance we know commonly as rust.
Is Rust The Same As Fire?
Rust is not the same as fire.
Though iron oxide is the end result, the rusting process takes place over a long period of time and with just a few molecules of iron at a time.
This means that it produces no noticeable heat and no flame both of which are required for “fire” to be present.
How Hot Does Iron Burn?
Iron once it is alight burns at temperatures up to 3600 degrees Celsius, that’s 6512 degrees Fahrenheit!
Does Fire Weaken Metal?
It’s not guaranteed but yes, fire can weaken the metal, and exposure to fire can reduce the strength, stiffness, and elasticity of steel and iron.
It may also result in buckling, twisting, and deflections of the metal itself.
Can An Iron Start A Fire?
OK, a household iron should not be confused with iron the metal but as this is a popular question, we’ll slot it in here.
New household irons are designed to switch themselves off (or for the fuse to blow) if they are placed on an item of clothing or ironing board and left switched on before they start a fire.
An older household iron without such protection could, in theory, start a fire by eventually heating the clothes or the covering of the ironing board enough that they burst into flames.
So, it’s probably best to unplug your iron before walking away from it, however, in the vast majority of cases – this won’t be necessary as most people will be using an iron with inbuilt safety precautions.
How Many Fires Are Caused By Curling Irons?
We’d also note that curling irons are not iron the metal either, but they do, according to the US Consumer Protection Safety Commission, start around 700 household fires a year!
So, please switch them off when they’re not in use.