Is Sulfur Flammable?

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Sulfur (or sulphur if you’re from the other side of the Atlantic) is a very common element, yet many people have probably never laid eyes on it. It’s best known for its distinctive rotten eggs smell, which occurs in many of its compounds, including those found in actual rotting eggs. But should we be alarmed when the stench of sulfur hits our nostrils is it a warning of an impending fire hazard? 

Sulfur can be flammable and catch fire easily, depending on the form. Sulfur powder will ignite easier than as a solid. The ignition temperature is between 160 and 190 degrees celsius (320 to 374 Fahrenheit).

Sulfur is actually more common than you might realize. It is important to understand the hazards that are associated with it. Take a look.

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Also read: What Makes Something Flammable?

What Is Sulfur?

burning sulfur

Sulfur is a non-metallic element that is the tenth most common element in the universe, by mass. 

On Earth, it’s the fifth most common element and it exists in an unusual molecular form of S8 which sees 8 sulfur atoms all bonded together in an octagonal pattern with bonds cycling around the formation. 

It was once known as “brimstone” and the name literally means “burning stone” and it’s been used since the most ancient times in both its pure elemental form and in mineral form. 

Today, it tends to be manufactured on an industrial scale by removing sulfurous contaminants from petroleum and natural gas products. 

Sulfur is, mainly, used to manufacture sulfuric acid, which is then used in many different types of fertilizer, but it can also be used in insecticides and fungicides and a use that was once common, but is now falling out of favor – the manufacture of safety matches and their match heads. 

Sulfur is essential for all forms of known life. In fact, there are some bacteria in the earth’s core that don’t use oxygen for their energy source but use sulfur, instead. 

In human beings it appears on three of our amino acids, two vitamins, and dozens of other organic compounds, it’s fair to say that we couldn’t exist without sulfur.

Is Sulfur Flammable?

Yes, as the name “brimstone” hints at, sulfur will very readily catch on fire.

The octet bonding structure of sulfur is easily broken under heat and sulfur has a low melting point, a low boiling point, and often sublimates (goes from solid to gas without passing through a liquid stage) when heated rapidly.

When burned with oxygen, it forms sulfur dioxide a gas that was a major contributor to the phenomenon known as “acid rain”. 

Sulfur in its ordinary form is not highly flammable, but it will catch fire. It has an ignition temperature of 160 to 190 degrees Celsius (320 to 374 Fahrenheit).

That’s hotter than the defined lowest temperatures for a substance to be considered flammable, but it’s fair to say that sulfur is readily combustible even in its usual form.

However, as with all substances, the conversion of sulfur to dust or powder dramatically lowers the flashpoint due to greatly increase the ratio of the surface area of the substance to its volume.

Sulfur powder is considered to be highly flammable and it needs storing carefully in order not to become a major fire hazard. 

Also read: Is Hydrochloric Acid Flammable?

How Hot Is Burning Sulfur?

Sulfur reacts very easily with oxygen but it’s not a particularly vigorous reaction and it produces 300 MJ/Kg mol of Sulfur. 

That’s “Megajoules” (a joule is the amount of energy required to raise the temperature of 1 gram of water by 1 degrees Celsius, a Megajoule is a million joules) and “Kg mol” is a complicated way of saying 32.07 Kg of sulfur (it relates to the amount of sulfur with the same number of molecules of sulfur as there are in 12 Kg of Carbon 12). 

That means, that in order to raise the temperature of 300 metric tons of water by just 1 degree Celsius, you would need to burn 32.07 Kg of sulfur!

There are 2,500 metric tons of water in an Olympic swimming pool. So, you would need to burn around 250 Kg of Sulfur to raise the temperature by a single degree in the pool!

Interestingly, in some situations, sulfur will melt first before it starts to burn, take a look:

Are The Fumes Flammable?

Yes, sulfur fumes are flammable, though given that sulfur becomes a gas at 440 degrees Celsius and it has a flashpoint of less than that, it is very unlikely that you would encounter “sulfur fumes” that hadn’t already caught fire in an oxygen-rich environment such as the air.

To create sulfur fumes that do not burn, you would need to do so under laboratory conditions with no oxygen present. 

Is Burning Sulfur Dangerous?

Burning sulfur products sulfur dioxide.

Sulfur dioxide plus water is sulfuric acid, a strong acid that can damage biological material (hence its involvement in acid rain which, until sulfur was removed from power plant fumes, used to severely damage trees and other forms of vegetation). 

Unfortunately, human beings are made up of water and our lungs, airways, and eyes are potentially all sites where sulfur dioxide can easily become sulfuric acid, even our skin has moisture on it that could react with the gas. 

This is dangerous. 

Does Sulfur Explode In Water?

No, sulfur does not explode in water.

But if you have sulfur, silver bromate, and water, that will cause an explosive reaction.

Fortunately, most of us don’t keep silver bromate laying around our homes, offices, or workplaces, so this is a minimal fire risk at best. 

Hazards of Sulfur

Sulfur is not particularly toxic in its elemental form and, in fact, by and large, exposure won’t cause you any problems. 

However, if you were to eat large amounts of sulfur it would likely upset your stomach and potentially even cause diarrhea.

Breathing in sulfur dust, rather like breathing in any other form of dust, can potentially irritate your airways.

There is also a possibility that sulfur dust might irritate your eyes or even your skin. 

Can You Get Sulfur Poisoning?

While you cannot get sulfur poisoning, sulfur dioxide poisoning is a real problem, it begins by causing a burning, painful sensation in your mucous membranes, it also causes crying, coughing, and wheezing.

It will also aggravate any pulmonary disease you already have such as COPD or asthma. 

If it gets on your skin, it can burn in the same way that frostbite burns. 

The good news is that it’s unlikely to happen to anyone outside of metal refinery operations, chemical works, and coal-based operations. 

It must be treated with oxygen supplements, bronchodilators, and even intubation if things don’t improve with the first two treatments. 

Can It Irritate Your Eyes?

Sulfur itself is a mild irritant to the eyes and can be washed out without any lasting damage.

Sulfur dioxide and sulfuric acid are very dangerous to the eye, on the other hand, and can cause severe damage to the cornea. 

If they get in the eyes, wash them with as much soapy water as possible and then see a doctor. 

What Does Sulfur Smell Like? 

Sulfur smells like rotting eggs, that’s because it’s a sulfur compound in rotting eggs that give them their smell.

It is worth noting that many sulfur compounds including hydrogen sulfide smell of rotting eggs too. 

You need to be careful when assuming because you can no longer smell sulfur that it is gone. 

In fact, hydrogen sulfide is a powerfully acidic gas that can burn out your sense of smell and over time, it hydrogen sulfide can kill you. 

It’s always best to check with a professional if you think there are sulfur or sulfur compounds in the air. 

How Do You Treat Sulfuric Acid Burns?

  • Rinse with mild soapy water within 1 minute of the burn taking place and then flush with mild soapy water for another 20 minutes. 
  • Make sure to use soap, water on its own makes a sulfuric acid burn feel hotter. 
  • Don’t, whatever you do, spray water onto the burn using a hard jet of water, it can further damage the area. 
  • Remove any clothing and jewelry near the affected area.
  • If burning persists after 20 minutes flush the area again for up to 15 minutes.
  • If the burns are severe, seek medical attention. 

Is Sulfur Good For The Skin?

Maybe. The science is still out on this one.

What we do know is that the skin can stand topical application of 10% sulfur creams for up to 8 weeks without irritation.

What they’re still investigating is whether sulfur’s natural anti-inflammatory and antibacterial properties can be used to prevent bacteria from building up on the skin and reduce the production of sebum in the skin. 

If it can do these things, sulfur may be a useful cure for acne. 


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