The apparent winding-down of the Syrian civil war, which has been raging for nearly two years, brings with it the risk that Syrian President Bashar al-Assad will fire chemical weapons at his own people.
World leaders of all stripes have come forward to vigorously denounce the weapons' potential use and issue threats about "red lines" that might provoke military action.
The chemical weapon that the Syrian military is believed to possess is sarin gas. Here is what you need to know about it:
1. Sarin is not naturally occurring. It was first developed in 1938 in Germany as a pesticide, according to the Center for Disease Control. Sarin is made by mixing isopropyl alcohol (also known as rubbing alcohol) and a compound called methylphosphonic difluoride, which is highly corrosive and is classified as a Schedule One substance by the Chemical Weapons Convention. This means this the chemical has no valid application outside of being used as a weapon.
Sarin was not the gas used in the Nazi death camps; that was hydrogen cyanide.
2. Sarin is odorless, colorless and tasteless, and approximately 500 times more toxic than cyanide. It is an especially volatile nerve agent, which means it attacks the body's nervous system and causes dysfunction in the communication between nerves and muscles. Sarin can be mixed into water or food, and it can remain active on clothing up to 30 minutes after exposure.
3. If Sarin gets into your system, you'll first experience a runny nose and tightness in the chest within seconds of exposure. Soon you'll have trouble breathing, and then you'll begin to lose control of your bodily functions. Then, your body will begin to convulse, and you'll fall into a coma. Death usually comes by way of asphyxiation, as you no will longer have control over your muscles and cannot breath properly. Even coming in contact with as little as half a milligram of sarin can cause brain damage or death.
4. The first known use of sarin as a weapon of mass destruction was during the Iran-Iraq war in 1988, when Saddam Hussein ordered that the Kurdish city Halabja be gassed. Approximately 5,000 people died instantly when around 20 aircraft dropped mustard and sarin gas, among other substances, on the 70,000 people living in Halabja. 75 percent of the victims were women and children, the BBC reported at the time. Those who didn't die developed severe respiratory or visual problems.
The second use of the gas was in 1995 in Tokyo, when the Japanese religious cult Aum Shinrikyo released sarin into the Tokyo Metro. Thirteen people died.
5. There is a treatment for sarin poisoning, but it must be administered almost immediately upon contact with the substance. The good news is people who experience non-lethal doses often make a full recovery, the CDC says.