Analysts believe Syria 's stockpile may include sarin , mustard and VX gases . Sarin gas is odorless and can cause convulsions , paralysis and respiratory failure . Mustard gas has a distinctive smell that makes it easy to detect by the human nose. One of the most horrific chemical attacks on a civilian area occurred 25 years ago , when Saddam Hussein unleashed chemical weapons in Iraq 's Kurdish city of Halabja . Analysts say the government 's increasing desperation may result in chemical weapons use .
Analysts believe Syria 's stockpile may include sarin , mustard and VX gases . Sarin gas is odorless and can cause convulsions , paralysis and respiratory failure . Mustard gas has a distinctive smell that makes it easy to detect by the human nose. Analysts say the government 's increasing desperation may result in chemical weapons use .