How Mustard Gas Works

Before we learn how mustard gas works, it's important to understand what a gas is in terms of chemical warfare. Just the word "gas" may lead people to think that the substance is a vapor. That's not entirely true. Gases in warfare can be any chemical substance, including gases, solids and liquids, and generally fall into one of three medical groups.

Mustard gas or mustard agent is a poisonous gas that falls in the first group, along with even more lethal chemical agents such as chlorine gas and sarin. Tear gas, for example, is a non-poisonous gas that falls in the second category. Although tear gas is an effective weapon against advancing soldiers, it has no deadly effects. The same can't be said about mustard gas.

Mustard gas, also called sulfur mustard, gets its name from its sometimes yellow appearance and mustardlike smell. It's referred to as a blister agent or a vesicant, and comes in vapor, solid or liquid form. Other blister agents include nitrogen mustard, lewisite and­ phosgene oxime.

Blister agents are no fun. Once in contact with an unsuspecting victim, they damage skin and internal areas such as mucous membranes inside your nose and throat. Mustard gas is an alkylating agent, meaning its chemicals destroy DNA and cells and liquefy tissue. In essence, mustard gas kills tissue and membranes in the areas it touches. Alkylating agents also are often used in cancer drugs.

As you might have picked up, mustard gas is very dangerous, especially compared to tear gas. If you measured mustard gas on a scale of one to 10, with 10 being the scariest, mustard gas would come in around a seven. Compared to Zyklon-B, the gas pellets used in gas chambers during the Holocaust, mustard gas seems tame. But that doesn't mean it hasn't caused its fair share of fatalities. A little bit later on, we'll look at some of the devastation mustard gas brought on during warfare.

Mustard gas comprises four elements found on the periodic table: carbon, sulfur, chlorine and hydrogen. The sulfur and carbon lend to the gaseous appearance and smell in both solid and liquid states. The exact molecular formula is C₄H₈Cl₂S.

In its crude state, mustard gas resembles used motor oil: heavy and sludgy. Because of a relatively high freezing point of 58 degrees Fahrenheit (14 degrees Celsius), mustard gas proved a less effective weapon in colder temperatures. It wouldn't spread throughout a large area, and it would fall to the ground before troops inhaled the deadly gas.

Mustard gas isn't something you find in nature. You won't discover it under a rock or buried in a mine shaft. The chemists who stumbled upon the compound quickly realized it could be deadly and even fatal if inhaled. Many credit Fredrick Guthrie as the first to synthesize mustard gas in 1860 , and Dow Chemical as the first company to produce it (during World War I) [source: Holland].

During World War I, a new style of fighting known as trench warfare pitted two armies close enough to each other that they could yell across the lines. But soldiers rarely ventured into the area between the two trenches commonly referred to as no man's land for fear of being gunned down, and battles would often settle into a stalemate. Chemical agents such as mustard gas became a way to break that uneasy deadlock.

Germany's first attempt at chemical weapons came in 1915 at the battle of Ypres in Belgium, in the form of chlorine gas. The gas cleared large sections of soldiers from the front lines, who fled once exposed, and ultimately killed 5,000 opposing troops [source: Encyclopaedia Britannica]. Chlorine gas burns the throats of its victims and causes death by as­phyxiation, much like smoke kills people during a house fire.­

The Germans used mustard gas for the first time during war in 1917. They outfitted artillery shells and grenades with mustard gas that they fired in the vicinity of the troop target. After encountering several attacks, the Allies referred to mustard gas as Hot Stuff or H.S., eventually dropping the S and just referring to it as H. By the end of the war, more than two dozen chemical agents had injured 1 million soldiers and civilians, killed 100,000 people and earned the well-deserved title of weapons of mass destruction [source: Encyclopeadia Britannica].

When you first encounter mustard gas, you may not even know anything is about to affect you. The best way to detect mustard gas is through smell. Like your experience in the opening section of this article, soldiers exposed to mustard gas had a hard time detecting a gas attack but noticed a funny smell. Even under heavy doses, however, their noses adapted to the smell quickly, giving them the impression that the gas had dissipated. Have you ever noticed you can't smell something, be it good or bad, after you've been sniffing it for a few minutes? The same principle applies during a mustard gas attack.

So one of the most dangerous aspects of mustard gas doubles as one of its most desirable attributes as a weapon. We know mustard gas is difficult to detect unless you're under a direct attack. It's even harder to notice in contaminated areas where the gas has settled. That posed a problem for soldiers walking through an exposed area that underwent an attack say two days earlier. The chemical agent would stay in the ground for weeks, depending on the temperature. The colder the ground, the longer the mustard gas would linger.

At the time the Germans began using the chemical, gas masks proved useless because mustard gas could penetrate the filters and mask housing. Not only that, but chemical suits hadn't been used yet, so mustard gas had the whole body to attack. And a little went a long way. One drop of the chemical weapon could cause skin burns on people within 10 cubic meters [source: Ward].

Mustard gas harmed and killed soldiers by the thousands and affected battle lines. Because of this versatility, mustard gas served as the most desirable chemical agent during World War I for both sides.

After a mustard gas attack, you might think nothing more about it for a few hours or even a day. Eventually the chemical burns would result in red spots forming on your skin that quickly turned into painful blisters. If you underwent a direct attack and inhaled mustard gas, it wouldn't take long to feel pain and swelling in your nose and throat as the blisters developed, sealing your airway.

The longer the exposure to mustard gas, the greater the damage it causes. Conversely, if you had a brief encounter, your body would heal faster, giving you a greater chance for survival. In some cases, victims experiencing a secondary exposure or multiple exposures develop hypersensitivity to the deadly chemical warfare agent.

You might experience some of the following symptoms after you inhaled or touched mustard gas [source: Centers for Disease Control]:

Some of the more serious delayed toxic effects and respiratory symptoms would take even longer to surface, needing anywhere from 24 to 48 hours to appear. This latent period played havoc with soldiers exposed during the war, rendering troops incapacitated, filling infirmaries, taking up valuable human resources, bogging down reinforcements and generally demoralizing soldiers.

Make no mistake, mustard gas can be lethal. But it doesn't kill quickly. Rather fatalities primarily result from secondary broncho-pneumonia. Approximately 2 percent of all casualties who wore a respirator died from their injuries in World War I, compared to a death rate of 50 percent of those exposed without a respirator [source: The Medical Front]. The highest number of fatalities occurred after the third or fourth day of exposure, with the most extreme cases taking up to three to four weeks [source: The Medical Front].

After an exposure to mustard gas during World War I, military doctors couldn't purge the effects of mustard gas in the body. Medical staff could treat the skin with ointments consisting of bleaching powder and white petroleum jelly and flush the eyes with saline solution, which helped some. For the more severe respiratory symptoms, medics treated patients with a menthol solution soaked into gauze administered through a metal breathing mask. This treatment alleviated dry cough but didn't cure the bronchial infection. For the most severe casualties, medics quarantined the affected patients and hoped for the best. In the end, early detection proved to be the best way to defend against the most serious respiratory effects.

For those who survived the short-term effects of mustard gas poisoning, there were a slew of other potential longer-term issues. Lung cancer, skin cancer, recurrent respiratory infections and bone marrow depression leading to leukaemia were all medical outcomes for those who initially survived mustard gas exposure.

When the Allies learned what they faced during a mustard gas attack, they quickly developed safety measures to limit casualties. The most significant breakthrough came with improved respirators. An adequate respirator protected the face and eyes using a sealed hood and clear glass to cover the head and face, but that still left the rest of the body exposed. Chemical suits didn't hit the scene until after World War I.

If you survived a serious mustard gas attack, you came out as one of the lucky ones. Maybe you lost your eyesight and even your voice, but you survived. Is the chemical agent still a wartime threat?

Mustard gas has seen action in other parts of the world since its introduction in World War I. The Japanese used mustard gas against the Chinese during World War II, while the United Nations accused Saddam Hussein of using the deadly gas against the city of Halabja in 1988 during the Iran-Iraq war to kill approximately 3,200 to 5,000 civilians [source: Grunden, The Guardian]

According to CNN, troops in the Gulf War may have dealt with mustard gas on several occasions. As many as seven U.S. Army divisions, or approximately 100,000 soldiers, may have been exposed during the war. While the total number remains unconfirmed, several soldiers who served during the Gulf War experienced symptoms in line with mustard gas exposure [source: CNN].

At the end of the Gulf War, the U.N. imposed strict sanctions against Iraq in order to eliminate the risk of future chemical warfare. In addition, the U.N. adopted the Chemical Weapons Convention, a global treaty that prohibits the use of chemical weapons. The only countries that hadn't signed the treaty as of 2007 were Angola, Egypt, Lebanon, North Korea, Somalia, Syria and Iraq [source: Encyclopaedia Britannica]. As long as chemical weapons exist, they will forever be a threat. We can only hope they don't fall into the wrong hands.