Well, they were warned
"Seven people have died in Homs after they inhaled a poisonous gas sprayed by government forces in a rebel-held neighbourhood, activists said.
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.
Residents said they did not know the nature of the gas sprayed.
"The situation is very difficult. We do not have enough facemasks. We don't know what this gas is but medics are saying it's something similar to Sarin gas," Raji Rahmet Rabbou, an activist in Homs, told Al Jazeera."
Here is a link that might be useful: link