Have you ever looked at the loaf of bread on your table and been afraid of it? Have you wondered if it could catch fire or maybe even explode? Probably not. But should you? Again, probably not. But what about the flour used to make that bread? Are the answers to those questions the same or different?
Flour has been around for thousands of years, and between wheat flour, corn flour, and rye flour, they form the foundation of staple foods for cultures all over the world. But, does our use of flour put us in danger? Well, not all by itself. What about when you add fire to the mix - is flour flammable?
The short answer is yes. Flour is flammable, it can catch fire, and it has caused explosions in many situations. But, as with most things, there is more to the story.
Flour - What Is It?
Flour is the powder resulting from grinding grains, usually wheat. Although, it can also be ground from nuts, roots, beans, and seeds. When talking about grains, we’re typically referring to the edible seeds harvested from cereal plants.
These seeds have three parts: the bran, the germ, and the endosperm. The bran is the protective outer layer of the grain seed. The germ is the part that grows into a plant. The endosperm acts as the food storage for the developing plant.
In order for grain to become flour, it needs to go through a milling process, which results in the grain being broken down into tiny particles. In the end, the three main parts of the wheat kernel (the germ, the bran, and the endosperm) are clearly separated and ready for use.
There are many types of flour. White flour (made from the endosperm only), also known as refined or bleached flour, and whole-wheat flour (made by recombining the endosperm with the germ and the bran once the germ is stabilized) are the most widely known.
Other flour variations and types, generally differentiated by gluten levels, include, but are not limited to: enriched, cake, pastry, all-purpose, bread, unbleached, self-raising, wheat, rye, corn, corn starch, peanut, potato starch, potato, and rice.
Flour is composed mostly of starches known as polysaccharides. These are a subset of carbohydrates whose core molecules consist of sugar molecules bonded together.
So, if you’ve ever put your marshmallow (aka sugar molecules) too close to the campfire, you know where this is headed!
What Is It Used For?
Flour is used for all types of cooking and baking, depending on what is being made and the type of flour being used.
A higher protein content flour will be harder and stronger, which will result in crusty or chewy breads. And a lower protein content will make for a softer flour, which favors cakes, cookies, and pie crusts.
Flour can be used to prepare an endless variety of foods (pizza, pasta, cookies, biscuits, etc.) in addition to thickening sauces and gravies. It can even be used for making play dough and paper-mâché glue!
Chances are pretty good you’ve eaten something with flour and more than likely made something with flour at some point in your life.
Is Flour Flammable?
Yes, flour is highly flammable. As previously mentioned, its main component is starch, which is a carbohydrate and can catch fire - think back to those marshmallows. Now if the flour stayed in a solid piece like the loaf of bread on your table, it wouldn’t be flammable and would probably not burn much at all.
However, flour particles are fine dust, and dust and powders tend to catch fire when floating freely in the air (aka oxygen) while in the presence of heat. This property is what makes flour combustible dust.
Since the dust particles are suspended and separated in air, when compared to their solid form, they take up more space which allows the flour dust to absorb and transfer more heat, therefore burning more easily.
So, particularly in a kitchen or any similar location that has an ignition source close by, since flour is flammable, any being used should be stored in tightly packed, airtight containers to reduce the chance of a large number of dust particles getting into the air.
What Causes A Flour Explosion?
Not only is flour flammable, but it can also explode. A flour dust explosion or combustible dust explosion is caused by those tiny suspended flour particles catching fire in the presence of heat, instantly igniting other particles nearby, and then expanding rapidly through the dust cloud with incredible force, resulting in an explosion.
What Else Is A Combustible Dust Hazard?
There are other kitchen items besides flour that are flammable or explosive. Almost any carbohydrate dust like powdered sugar, non-dairy creamer, pudding mix, powdered milk, corn starch, and cocoa will explode if ignited. And this is just a small number of other items - the list goes on and on.
Outside the home, things like grain, wood, coal, and metals could have the potential for a dust explosion. Similar to flour, metals, for example, may not typically be combustible when in a more compact or solid form, but they can burn or explode if the particles are the right size and in the right concentration while mixed with oxygen and a heat source.
Is Flour A Risky Fire Hazard?
In the home, the risk of flour dust starting a fire or causing an explosion is minimal because the quantity of flour being used at any one time is typically small. In addition, the way it is used, like being mixed with water, doesn’t lead to large clouds of dust particles.
However, in industrial settings, like grain mills and processing plants, the risk of an explosion is much higher. These types of facilities handle a substantial amount of flour on a regular basis and are typically large buildings with the kind of spaces that can easily enable the powder to separate and form sizable dust clouds.
In addition to the dust created during general processing, large bags can be dropped while being moved around the mill, the powder can pile up in storage bins and silos, or there could be dust accumulation in rail cars.
These are the settings and situations that typically pose the biggest explosion hazard, since any ignition source, like a spark or wayward flame, in these environments, could be a trigger. And if a fire starts in one of these places, not only is an explosion likely directly in the area with the dust accumulation, but given the size of the mills and proximity to other buildings, the risk of a secondary explosion exists as well.
Unfortunately, grain dust explosions have occurred at mills around the world and when you hear about them, they usually involve devastation and loss of life. Luckily, the severity of those explosions has lessened over time as more safety measures have been put in place.
How To Prevent Flour Dust Explosions
Whether at home or in an industrial setting, the approach to safety is the same - keep the flour as confined and tightly packed as possible to reduce or eliminate the possibility of dust clouds forming and keep flour away from heat and flame sources.
There is no need to fear using flour in the kitchen at home since the possibility of fire is minimal given the quantity of flour involved and the lack of a confined space. And any fires that happen would most likely be minor and easy to extinguish.
Just remember - if there is no dust cloud, there is no explosion!