There's not much info so this will be a short diary, but this is grave:
Seven people have died in Homs after they inhaled a poisonous gas sprayed by government forces in a rebel-held neighbourhood, activists said.More info at al-Jazeera
Activists also told Al Jazeera that scores of others were affected in al-Bayyada neighbourhood. Side effects reported include nausea, relaxed muscles, blurred vision, and breathing difficulties.
It should be noted that there is no claim of responsibility, the assumption is that since the attack was on a rebel area it was released by government troops or Assad loyalists. This is the most likely scenario.
That said, sarin has been used in the past in a terror attack on the Tokyo subway in 1995, so this is not necessarily from the Syrian Government stockpile.
This could also be a false-flag attack by rebels or other interested parties like al-Nusra Front, the Syrian branch of al-Qaeda who would like to see the rebels receive military assistance from the US.
Whatever the source, this opens a new and very grave chapter in the liberation of Syria.