I will let you read this
https://en.m.wikipedia.org/wiki/Destruction_of_Syria's_chemical_weapons
http://www.lefigaro.fr/internationa...-en-syrie-histoire-d-un-massacre-de-masse.php
11 chemical attacks, of which 10 attributed to Assad.
Chlorine is readily available (for the chemical industry) and chemical weapons are very easy to hide.
"Syria never signed the Chemical Weapons Convention, the current international treaty against the use of poison gas, but it did sign the 1925 Geneva Protocol, which banned the use of chemical and bacteriological warfare, according to the international Organisation for the Prohibition of Chemical Weapons (OPCW.)"
http://www.cnn.com/2017/04/05/middleeast/syria-sarin-chemical-weapons-explainer/
https://en.wikipedia.org/wiki/Use_of_chemical_weapons_in_the_Syrian_civil_war
Also, 90% of the attacks or more are carried against enemies of the Syrian Army, half of the ones reported by the Syrian are not evidenced, and if you go further in the reports, the ones used against the Kurds, the rebels, Aleppo... match the government stockpiles. What a coincidence, must be the UN, the OPCW must be biased.
And a proof that Assad has always been lying:
But yeah, Assad is an angel, he would never have done that, he threatens just for fun. The modus operandi is the same than the ones before.