I'm in Construction, so lots of equipment that considered hazardous. Lifting equipment, which we pre-plan using qualified riggers. Quickie saws & nail guns require job hazard analysis prior to use.

Chemical loading and unloading. We supply full air assisted respirators and special chemical suits. We also have two huge boilers-which also takes months of training to do the right things.

The list for the refinery is very long. There’s a lot of specialized training, but I’d say the most important item was keeping awareness training up to date for the entire population who may have need to work or simply enter the plant boundary.

I guess the most significant area would be the hydrofluoric acid catalyzed alkylation unit. The control measures for that area are extensive, and considering that I’m curious if “most hazardous” should really be defined as the area where the hazards are least known or least controlled. For example, if an office has a poor safety culture but the grounds crew does, then the stairs (no one uses the handrails) may be the most dangerous part of that building and not the chain saws used to trim the trees.