Russia has struck a warehouse in Ternopil, Ukraine which was storing Ukraine Military Weapons including missiles. Apparently there was also a large store of liquid Chlorine, which is now leaking, creating a Chlorine gas cloud.
The gas cloud is being carried by prevailing winds to the west / northwest. It has already traveled about 150km toward the Ukrainian city of Liviv. Once is passes LVIV, next stop: Poland.
NATO long ago made clear that if Russia utilized nuclear weapons in Ukraine, and fallout reached a NATO country, NATO would consider the fallout "an attack" and enter the Ukraine war.
Now, we have the chemical Chlorine, in an uncontrollable gas cloud, moving west / northwest toward LVIV and thereafter, Poland. What will NATO do?