Will be interesting to hear about exactly what went wrong.
With an odor threshold of 1 ppb and a rat LC50 of 675 ppm one would assume one usually gets adequate warning to escape? Unless the discharge was unusually large or you were right around it or got trapped / boxed in.
A quick lookup shows most respirator cartridges being good enough to allow escape at most concentrations.
Somehow all the holes in the cheese just lined up on this one. Sad.