( CNN ) -- With the strength of Bashar al-Assad 's forces diminishing in Syria 's civil war , global fears are mounting that Syria might unleash chemical weapons to quash the country 's uprising . The government insists it would never use chemical weapons on its own people . But world leaders say Syria 's desperation could lead to even more tragedy in the war-torn country . So what exactly are chemical weapons , and what could they do to the human body ? A primer : . -- What kinds of weapons are we talking about ? Military analysts believe Syria may have one of the largest stockpiles of chemical weapons in the world . Specifically , the supply could include sarin , mustard and VX gases . U.S. intelligence indicates Syria has mixed chemical compounds needed to make sarin -- a deadly agent that can quickly kill thousands . Opinion : Do n't wait for Syria to cross the 'red line ' -- How do these chemicals affect the body ? Sarin gas is an odorless nerve agent that can cause convulsions , paralysis and respiratory failure . Nerve agents are the most toxic and rapidly acting of the known chemical warfare agents , according to the Centers for Disease Control and Prevention . Sarin quickly evaporates from liquid to vapor form and disperse into the environment . It also mixes easily with water and can poison a water supply . VX is another nerve agent that can be lethal when inhaled . It can also be dispersed in a liquid form ; even a few small drops on the skin can lead to the same effects as sarin gas . `` Compared with the nerve agent sarin ( also known as GB ) , VX is considered to be much more toxic by entry through the skin and somewhat more toxic by inhalation , '' the CDC said . Mustard gas -- also known as sulfur mustard -- leaves chemical burns on the skin , eyes and even the lungs when inhaled . It was commonly used in World War I . While mustard gas can be fatal , it also can disable victims and can cause cancer or permanent blindness . Syria 's endgame in sight as rebels advance . -- How are chemical weapons deployed ? Syria could deliver chemical agents through a variety of ammunition , such as bombs dropped from aircraft , Scud surface-to-surface missiles , artillery shells or rockets , according to Jeffrey White of the Washington Institute for Near East Policy . -- How long do the dangers linger ? A person 's clothing can emit sarin for about 30 minutes after exposure to sarin vapor , which can lead to exposure of other people , the CDC said . Sarin can also be ingested though contaminated food . VX gas evaporates very slowly , at about the same rate as motor oil . As with sarin , it can also be emitted from clothing for up to half an hour after exposure . Sulfur mustard , however , can stay in the environment for a few days under average weather conditions and up to months under very cold conditions , according to the CDC . -- How devastating can chemical attacks get ? 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 . The attack left thousands dead and thousands more wounded . -- What 's the risk of Syria using chemical weapons on foreigners ? While Syria has vowed it would never use `` unconventional weapons '' or weapons of mass destruction against its citizens , it gave a stern warning to other countries who might try to intervene militarily in the Syrian conflict : . `` All the stocks of these weapons that the Syrian Arab Republic possesses are monitored and guarded by the Syrian army . These weapons are meant to be used only and strictly in the event of external aggression against the Syrian Arab Republic , '' Foreign Ministry spokesman Jihad Makdissi said in July . But with no end in sight to Syria 's 21-month conflict , some are n't so sure Syria will keep its promise . `` For the first time in the history of the Chemical Weapons Convention ( CWC ) , which entered into force in April 1997 , there are serious concerns that chemical weapons might be used , '' said Ahmet Uzumcu , director-general of the Organisation for the Prohibition of Chemical Weapons . U.S. President Barack Obama warned Syria that any deployment of chemical agents would be catastrophic . `` The use of chemical weapons is and would be totally unacceptable , '' Obama said this week . `` And if you make the tragic mistake of using these weapons , there will be consequences , and you will be held accountable . '' CNN 's Tom Foreman , Barbara Starr and Tim Langmaid contributed to this report .
Analysts believe Syria 's stockpile may include sarin , mustard and VX gases . Sarin gas is odorless and can cause convulsions , paralysis and respiratory failure . The Syrian government insists it would never use chemical weapons on its own people . Analysts say the government 's increasing desperation may result in chemical weapons use .