ISIS launching chemical attacks at Kurdish forces?

Thanks to Ronald for the link!

via el-ahkbar news.

According to Al-Alam News Network reporter ,Many People injured and Poisoned by ISIS Chemical attack on the village of Bashir.
ISIS Targets Bashir Village by at-least 7 missile filled by Sarin and Chlorin Gas.
The village of Bashir, south of Kirkuk city, was cleared of the Islamic State (ISIS, ISIL, IS and Daesh) by the Kurdish Peshmerga and Shiite forces  – Hashd al-Shaabi –  Sunday.
Bashir, 20 kilometers south of Kirkuk city, is a predominantly Shiite town that fell to ISIS last year.
Pockets of ISIS resistance still exist around Bashir village.

Chemical weapons.  Geez.  I hated the tear gas chamber I can't imagine trying to fight on a contaminated battlefield.

Question.  If the US has Special Ops embedded in Kurdish forces and those forces are gassed then how do you handle (let's say) a Special Forces A-Team that suffers casualties?  Of course you take care of the men, but what do you do moving forward?  Once the use of chemical weapons against US forces would justify a nuclear response.  That most certainly is no longer the case so what do you do to keep ISIS in the cage with this?

And if you can't then what's to keep them from trying to develop more persistent and deadly chemicals to use against major population centers?