It looks like the Douma gas attack story was a concoction by the US government, aided and abetted by the Organization for the Prohibition of Chemical Weapons (OPCW). From Caitlin Johnstone at caitlinjohnstone.com:
You wouldn’t know it from today’s news headlines, but there’s a major scandal unfolding with potentially far-reaching consequences for the entire international community. The political/media class has been dead silent about the fact that there are now twowhistleblowers whose revelations have cast serious doubts on a chemical weapons watchdog group that is widely regarded as authoritative, despite the fact that this same political/media class has been crowing all month about how important whistleblowers are and how they need to be protected ever since a CIA spook exposed some dirt on the Trump administration.
When the Courage Foundation and WikiLeaks published the findings of an interdisciplinary panel which received an extensive presentation from a whistleblower from the Organization for the Prohibition of Chemical Weapons (OPCW) investigation of an alleged 2018 chlorine gas attack in Douma, Syria, it was left unclear (perhaps intentionally) whether this was the same whistleblower who leaked a dissenting Engineering Assessment to the Working Group on Syria, Propaganda and Media this past May or a different one. Subsequent comments from British journalist Jonathan Steele assert that there are indeed two separate whistleblowers from within the OPCW’s Douma investigation, both of whom claim that their investigative findings differed widely from the final OPCW Douma report and were suppressed from the public by the organization.