Most people probably don’t pay that much attention to the amount of cotton in their day-to-day lives. Even if most of their clothes and much of their fabric coverings are made from cotton, it’s just there. Yet, perhaps we should pay more attention, after all, people who run laundrymats are very aware that it’s possible for the cotton to spontaneously combust!
Cotton will catch fire and burn at around 410 degrees Fahrenheit (210 Celsius). Cotton will spontaneously combust (auto-ignition temperature) around 764 degrees Fahrenheit (407 Celsius), which means that it will catch fire and burn somewhat easily.
So what does this mean in the real world? How easily does cotton catch fire? Lets take a look.
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Does Cotton Burn Easily?
It depends on how much cotton that you have.
Cotton such as that in a t-shirt or your average load of laundry will burn pretty easily.
210 degrees Celsius isn’t the kind of temperature you get on a hot, sunny afternoon, thankfully but it’s not a particularly remarkable temperature either.
The reasons that laundry services fear the autoignition point of cotton is that it’s easy for a tumble drier or iron to reach that kind of temperature and before they know it, the clothes are on fire and it’s going to be hard to put it out.
In fact, the normal “high” setting on a tumble dryer tends to be around 190 degrees Fahrenheit, when cotton is tightly folded and left over the top of a dryer, it can very quickly raise the temperature of the dryer by blocking the vent – and then the cotton could burst into flames.
However, one unusual property of cotton is that the more densely packed it is, the less it appears to burn.
This is asserted by Wakelyn and Hughs in their paper for Fire and Materials, Evaluation of the Flammability of Cotton Bales.
How Flammable Is It Really?
We’ve already seen that the kind of cotton that we have laying around the home is pretty flammable but this may not be the case for cotton bales.
This is due to the oxygen available.
Remember that all fire needs heat, fuel, and oxygen in order to sustain a fire. When cotton is packed tightly in bales, there is not enough space for oxygen and it will take much higher temperatures to sustain the combustion process.
This is the same reason that you don’t start a campfire with one giant log, as it’s too hard to get the fire started.
You use small sticks or kindling so there is more air space and less heat is needed to get the fire started. As the fire heats up you can add bigger and bigger logs due to the increased heat.
In fact, Wakelyn and Hughs cite three studies that demonstrate conclusively that baled cotton, when baled to a standard as laid down in the United States (there is some international variation which was not part of the study) is not particularly flammable.
Their research shows that though the government, via the Department of Transportation, insists that cotton bales be labelled “flammable solids” (a designation which indicates a high-level of risk and thus, affects how bales must be stored or transported), there is no scientific basis for this.
Their paper thus calls for industrial cotton bales to have this status removed.
At What Temperature will It Catch Fire or Ignite?
The autoignition temperature of cotton, as stated previously, is 407 degrees Celsius. This is pretty hot, but it still behooves us to take sensible precautions with cotton.
This is especially true of loose cotton garments in close proximity to drying equipment, ironing equipment and even open fires.
In fact, I have responded to a fire caused by cotton clothes set in front of an electric heater (at a reasonable distance away) to dry out on the back of a chair. This lead to an apartment full of smoke when they caught fire after drying out.
Also read: What Makes Something Flammable?
Does It Burn or Smolder?
We’re not being facetious here. Cotton can do both.
In general terms, cotton garments and materials in every day use are likely to burn.
Cotton, rather like paper, is made of cellulose fibers which as we know, are flammable, and once alight they generate their own heat (through the combustion of hydrogen and carbon in the cellulose) to sustain a flame.
Thus, if you were to drop a match in your underwear drawer, assuming your underwear was made of cotton, you would probably need a fire extinguisher or some water to put out the resulting blaze, it wouldn’t just extinguish itself (though you might be able to close the drawer to remove the oxygen source from the fire if all else failed).
However, once again, those pesky cotton bales won’t play ball and the paper from Wakelyn and Hughs shows that densely-packed cotton fibers don’t burn so much as they smolder instead, and this is the reason that they believe the flammability of cotton bales has been overestimated.
They showed that up to temperatures of 400-595 degrees Fahrenheit that the bales would smolder but not ignite.
This is, of course, a much higher temperature than the usual temperature that loose cotton will burn at.
Also read: Are Spider Webs Flammable? Sorta…
Is It Ever Fire Resistant?
No, cotton is not at all fire resistant.
Though it is possible to add some fire resistance by blending cotton, even if it were present in only tiny quantities in a garment – we’d be reluctant to rely on any supposed fire-resistant properties.
Also read: Is Nylon Flammable? Kinda…
What About 100 Percent Cotton?
We have heard that there is a dangerous rumor that pure cotton is fire-resistant, but it is not true. It is less likely to burn than some fabrics, like polyester, but it can still catch fire in some instances.
Cotton is definitely flammable. Cotton burns at 410 degrees Fahrenheit, though if it is in bale form, it might not burn but rather smolder at temperatures up to 600 degrees Fahrenheit. Thus, cotton is a flammable material that should be kept safe to avoid accidental fires at home or in the workplace.