Syrian Chemical weapons.

According to this administration that is our line in the sand, if President Assad of Syria uses chemical weapons then America will act against him.

Chemical Weapons, the name alone strikes fear and terror, movies and video games portray them as weapons of horrifying effectiveness and destruction.

But are they really that bad?

The answer is both yes and no, the after effects of Chemical weapons can be quite terrible, but the practical effects in warfare are surprisingly limited, even in WW1 the weapons were used more for fear then actual effectiveness. Wind can send the clouds of gas back at your own men and weather conditions can often reduce the effectiveness of the gas itself. To be effective with Chemical weapons even in the best of conditions you have to use a lot of them, a single Gas shell will be less effective then a High explosive one, to effectively use Chemical weapons you have to drop massive amounts of it down upon the target area and unless your soldiers are outfitted with Chemical suits you will have to wait some time before attacking that position.

So, why would Assad use Chemical weapons to fight the revolutionaries?

The answer is that he wouldn't, or at least wouldn't order his men to use them, especially when he knows that the US is looking for any opportunity to get in on the war.

So who would use them? Well no modern commander would choose gas weapons over any other type of weapon but a desperate officer might use anything at his disposal no matter how ineffective it is. On the same token the Rebel forces fighting against Assad are in league with many terrorist organisations, including Al-Qaeda and the Muslim Brotherhood. For them the places America has "Liberated" are gold mines of anti-American people who will join them.
The Syrian rebels are also supported by America in everything but us sending actual soldiers though many in Washington are itching to send more.

While Assad may not have a reason to order Chemical attacks the Rebels do, if the rebels can launch a Chemical attack and blame it on Assad's men then not only will America come to their aid but most of NATO will as well. For the terrorist factions it will mean a repeat of Libya.

The American Government also has a reason to use contacts in the Rebel army to launch a Chemical strike and blame it on Assad, before getting involved militarily.
First is profit, war is profitable.
Second is that taking out Syria would be a first step to taking out Iran.
Third America is divided and the public is getting sick of politicians, but nothing unites the people better then a moral crusade.
Fourth, Americans are calling for a reduction in our overseas presence, showing them something horrible and then saying "This is what happens when we don't get involved! Children die!" Is a way to counter that and enable them to retain their power complex.
And Fifth, Russia has a military port on loan with the Syrian government for it's Mediterranean fleet and is an friend of Syria. If the rebels win then America could take over the use of the port and Russia would lose an ally and a valuable port.

While I can not say for certain that Assad will not use Chemical weapons I have to conclude that it is highly unlikely that he will do so and if there is an attack it will likely be a false flag to justify American intervention.