1. to put people to sleep
   to hurt or kill humans
2. to stop killer bears

Chemical weapons have ill intent. They're meant to hurt or even kill people, and many of them work in insidious and terrible ways.

1. firearms
   conventional explosives
2. weapons of mass destruction

They are WMDs -- weapons of mass destruction. Chemical weapons can easily be spread over large geographic areas, killing indiscriminately.

1. sodium chloride
   nerve gas
2. methane

There are many types of chemical weapons, such as nerve gas. Even common pepper spray and tear gas are considered chemical weapons.

1. American Revolution
   World War I
2. Gulf War

So your enemy is hiding in miles of deep trenches and there's no way to uproot them. How do you attack? With terrifying poison gases, that's how. And that's one more reason World War I was so awful.

1. by suicide troops with hoses
   using huge planes
2. with the wind

During World War I, both sides used the wind to disperse poisonous gases. As you can imagine, this plan often backfired the worst possible way … because when the wind suddenly shifted, you were in big, big trouble.

1. pepper spray
   mustard gas
2. vinegar

Sulfur mustard is mustard gas. It was widely used in WWI, and it caused all sorts of grievous injuries.

1. garlic
   baby's breath
2. violets

WWI soldiers always knew when mustard gas was present. It had distinctive smell of garlic, or even horseradish. For many, it became the smell of terror.

1. laughing gas
   tear gas
2. cadmium sulfide

When it comes to riot control, CS gas is a standard tool in America. It's better known as tear gas … and you don't want to experience it.

1. hallucinations
   blistering
2. extreme laughter

Mustard gas exposure causes awful blistering of the skin. Inhale too much of this scary stuff and even your lungs will erupt in painful blisters.

1. They could taste it from miles away.
   They could feel it on their skin.
2. It was a visible green cloud.

You can imagine the feeling of horror -- watching a giant green cloud roll across no man's land. But the good thing about a chlorine attack was that you knew it was coming, and it gave you time to find your gas mask.

1. handheld sprayers
   artillery shells
2. hot air balloons

In January 1915, Germany blasted nearly 20,000 artillery shells containing a type of tear gas. But it was so cold that the chemicals were frozen … and thus, didn't really work.

1. burns
   blistering
2. asphyxiation

Chlorine, in high concentrations, can cause asphyxiation. Because the gas is heavier than air, many WWI troops avoided harm by climbing higher in their trenches.

1. tear gas
   nerve agent
2. choking agent

VX ominously stands for "venomous agent X," and it's an infamous nerve agent. Developed by the British following WWII, it's been used in several high-profile attacks.

1. about 1%
   about 60%
2. nearly 100%

Mustard gas is incredibly painful and can lead to all sorts of health problems. But only about 1% of exposed people die.

1. many, many more
   about the same
2. far fewer

By the time WWII rolled around, few commanders wanted to risk the political fallout of using more chemical weapons. So although fewer of them were deployed in WWII, they did still see some use.

1. It made them more effective.
   It banned them.
2. It demanded a 10% reduction in stockpiles.

Since the Hague Convention in 1899, chemical weapons have essentially been banned. But of course, rules are made to be broken.

1. radon
   mustard gas
2. tear gas

In the horrifying Halabja chemical attack, Hussein's men launched mustard gas at Kurdish civilians. It was the biggest chemical attack on innocents in human history.

1. sarin
   phosgene
2. chlorine

Mustard gas might be the most notorious of the WWI-era chemical weapons. But it was phosgene, which has the pleasant smell of freshly cut grass, that killed nearly 9 out of 10 troops who died from chemical weapons.

1. reddish
   yellow
2. colorless

Unlike some gases, say, chlorine, phosgene is colorless. So in wartime, it can creep up on its victims.

1. Jacksonville
   Tokyo
2. Des Moines

In 1995, crazed cult members unleashed a sarin gas attack in the Tokyo subway system. More than a dozen people died and more than 1,000 were injured. The cult may have initiated the attack in part to jump start the apocalypse.

1. causes eyes to close
   hours of sneezing
2. delirious happiness

Pepper relies on capsaicin from pepper plants. It might make spicy food fun, but when it's sprayed directly in your eyes it forces them to close. It will also make you scream.

1. about 60 minutes
   about 1 day
2. about 1 minute

In WWI, hydrogen cyanide was used in some limited instances, and indeed, at high concentrations it can kill in just one minute. But because it's lighter than air it tends to quickly disperse into the atmosphere.

1. to initiate lawsuits
   to cause paralysis
2. to kill plant life

Agent Orange gained infamy during Vietnam, when the U.S. used countless gallons of it to defoliate huge swaths of the jungle. But it also caused horrible side effects in both the natives and American troops.

1. It remains in the area for a while.
   It almost immediately disappears.
2. It permanently contaminates the location.

Unlike many chemicals, mustard gas doesn't just immediately drift away. It clings to the environment thanks to its oily consistency … and weeks later, it can still harm you.

1. One that kills at least two people
   One launched by computer
2. One that's harmless until the chemicals are combined

Unitary chemical weapons are deadly just as they are. Binary weapons, however, contain more than one chemical agent, and they aren't deadly until they are combined in battle.

1. stockpiled them in Africa
   launched them into space
2. dumped them into the ocean

"Well, we have millions of gallons of chemical weapons from Hitler. Let's just throw them all in the ocean. No one will know." So that's exactly what they did.

1. to cause instant cancer
   to obliterate enemy lines
2. to harass

Mustard gas is lethal in very high concentrations … but it's hard to generate those concentrations on an active battlefield. So in WWI, this chemical was mostly used to frighten or harass the enemy.

1. "Chemical Ali"
   "Mustard Man"
2. "The Harvester of Souls"

Ali Hassan al-Majid led the 1988 chemical attack on Kurdish civilians, earning him the nickname "Chemical Ali." He was captured and convicted of war crimes in 2010 … and then executed by hanging.

1. roughly 100,000
   about 2 million
2. at least 5 million

Both sides deployed ungodly (and inhumane) amounts of chemical agents in WWI. In many places, the weapons worked -- about 100,000 troops died from these attacks.

1. death
   increased stamina
2. lunch

Because you can buy pepper spray at retail outlets, many people think it's relatively harmless. But pepper spray is very hard on the human body … and in some cases, it's been linked to deaths.