Poison gas was used by German and Allied forces during WWI

The first use of lethal chemical weapons was in Belgium in WWI

Pueblo, United States - At a hi-tech military installation on the windswept prairie of southern Colorado, a small army of workers in protective gear, assisted by precision robots, is training to destroy one of mankind's most vile inventions: chemical weapons.

"Chemical agent destruction is a hard role. It's a high hazard operation," says project manager Kim Jackson.

"We have explosion hazards, and we also have agent hazards. That means anyone who might be exposed to the blister agent. So we spend a lot of our time with our personnel on training to ensure that our workforce is ready to complete chemical weapons destruction."

The facility's official name is the Pueblo Chemical Agent Destruction Pilot Plant. In the 1940s, as the US entered World War II, the military created a huge stockpile of chemical weapons, mainly in the form of artillery shells.

Syria: Chemical weapons attack

Fortunately, neither side used chemical weapons against enemy troops during the war. So the ageing munitions - primarily mustard gas - sat for decades inside concrete and earth-covered "igloos" at the Pueblo Chemical Depot.

In the 1990s, the US and most other nations signed a treaty pledging to destroy their chemical weapons. After many delays, that is what is happening now to the mustard gas shells stored at Pueblo.

"Mustard rounds were introduced in World War I," Jackson told Al Jazeera. "And to think here we are 100 years later completing destruction of those chemical weapons."

Chemical weapon history

Poison gas was used by both Allied and German forces from 1914 to 1918, killing about 80,000 soldiers and wounding one million more. Mustard gas, chlorine and phosgene were not particularly effective on the battlefield, but they terrified and demoralised men in the trenches.

Mustard gas can cause severe burns, blindness, suffocation and a slow, painful death.

One of the soldiers wounded by mustard gas was a young corporal in the German Army named Adolf Hitler.



After the so-called War to End All Wars, use of poison gas was outlawed under the Geneva Convention of 1925. But chemical weapons continued to be used by imperialist powers and dictatorial regimes.

The British used chemical weapons against Bolshevik troops in southern Russia, and against insurgent tribes in Iraq in the 1920s.

Winston Churchill, then secretary of state for war in Britain, was a firm advocate of chemical weapons.

I am strongly in favour of using poisoned gas against uncivilised tribes. Winston Churchill

"I am strongly in favour of using poisoned gas against uncivilised tribes," Churchill wrote in an official memorandum.

Italian dictator Benito Mussolini used gas against the Ethiopian army in the 1930s; Egyptian leader Gamal Abdel Nasser used it in his intervention in the civil war in Yemen in the 1960s; and Saddam Hussein used sarin gas against Iraqi Kurdish rebels and Iranian soldiers in the late 1980s, and also against the rebellious Iraqi Shia population in 1991.

Most recently nerve gas was used against civilians in the civil war in Syria in 2013. No official allocation of responsibility for the gas attack has been made.

Destroying mustard gas

Some 780,000 mustard gas shells are stored near the Colorado plant. That's the vast majority of the remaining US stockpile. Workers are practising on dummy shells exactly like the artillery that was manufactured during World War II.

Full scale weapons destruction will begin in October. Currently, Jackson is running rigorous tests of both equipment and personnel.

"They never know what I'm going to throw at them," she says, smiling. "We use different contingencies, such as a medical event, a chemical spill, or a loss of equipment, and they have to respond."

Site manager Bruce Huenefeld told Al Jazeera it's an extremely disciplined, procedural process. "It's very methodical. My job is to worry about making sure we do this operation safely and the workers are protected."

Each shell will be carefully unpacked and have its explosives removed, then repeatedly checked for leaks. The round is then taken apart, soaked in neutralising chemicals, blasted with high pressure water, and baked in ovens to strip away every trace of poison.



In a separate building at the site, some live shells that are leaking or have been damaged are already being destroyed with controlled explosions.

Workers clad in protective clothing carefully load rounds into a thick steel cylinder, constantly checking items off a lengthy list. Inside the cylinder, explosive charges neatly split the shells in two, which are then treated with chemicals.

"The mustard gas is inside the destruction system vessel. That's neutralised with monoethanolamine," Huenefeld says. "We rotate the vessel and typically in no more than an hour the monoethanolamine has completely broken down the mustard agent."

Only experienced need apply

Engineers working on the destruction project are highly trained.

George Robinson has spent 30 years neutralising chemical weapons and other types of munitions. He was one of the technicians who destroyed chemical weapons and precursor chemicals given up by Syria in 2014.

Those substances were destroyed onboard a US navy vessel in the Mediterranean Sea.

"The challenging part was the fact that the system was a land-based system that we put on board the ship and tested on the ship," Robinson says.



While the engineers and chemists who carry out this dangerous, painstaking job do not often talk about the broader historical or moral aspects of their work, weapons engineer Jon Miller sees it is as a deeply satisfying task.

"Chemical weapons are about the worst thing going," Miller says. "They're dirty, they're nasty. So really, getting rid of them, in my opinion, is kind of an important thing."

Destroying the stockpile will take at least four years at a cost of $4.5bn.