I had an idea about the chemical.  It's not an inhaled gas, but a contact one, which can linger like nerve gas does, with even trace amounts causing the effect.  And with the whole Burning Man festival contaminated, a lot of people would come into contact with it when the people and their stuff go home.<br/><br/>This also would explain why Daibuster was affected despite having Life Support.  It clung to her force field and then got on her when she turned it off later.