Comment: I've seen no evidence produced by Assad or Putin that supports their claim that is was accidental dispersion caused by blowing up an amunition dump.   I  did read the theories from western writers, none had any on-site evidence to work from.

Accepting that the administrations and the military are willing and able to obfuscate the truth,  is very rational choice.   Don't assume guilt, don't assume innocence would be my mantra when it come to most powerful institutions, (the White House and Pentagon both qualify in the public domain)