This is my job:
I was finally allowed to photograph my job as a rescuer and safety officer in sour gas plants/field. The lease this happened on I can't say, but it was a flare knockout vessel 15' underground with a 20" diameter and 8' entry chute. It normally contains benzenes/H2S/NORMS/and a mildly corrosive sludge which traps it all until it's stirred up.
The guy with the particulate mask went in after an initial gas check, but what we didn't know was further up the pipeline they were pressuring up a line that wasn't blinded... allowing toxic hydrogen sulphide into a vent line, which caused the entrant to become overcome and fall into the mildly corrosive sludge in the bottom of the tank. I'm the blue suited shmuck that went in to rescue him: he's alive and kicking, and the big thanks go to my team who were on the ball and rescue time was under 5 min and he was revived by the EMT onsite.
Once I went in we weren't allowed to take pictures in case it was a retieval.