[0x07c0]

I did not watch you link, but many modern chemical weapons are binary compounds. Meaning the two compounds has to be mixed to get the final weapon. This makes leaking etc, not as big problem as leaking of actual chemical weapons...

https://en.wikipedia.org/wiki/Binary_chemical_weapon

[jacquesm]

Once things start leaking you're a very small step away from them mixing accidentally.

Unless containment has been set up in such a way that this is a geographical impossibility (for instance, on two sides of the Rocky mountains to stop accidental mixing in groundwater).