The hazard
Well sites put flammable gas and liquids, possible toxic gas like hydrogen sulfide, high pressure, heavy equipment and several crews in one small area. Conditions can change fast, and one missed step can lead to a fire, an explosion or a toxic release. Knowing the hazards and looking out for each other is how everyone gets home.
The action
With limited exceptions, each container of hazardous chemicals on location must be labeled, tagged or marked with at least the product identifier and general information about its hazards. Labels on incoming containers must not be removed or defaced unless the container is immediately marked with the required information (29 CFR 1910.1200(f)(9)). If you find an unlabeled drum, tote or bottle, do not guess what is inside. Stop and ask. (29 CFR 1910.1200(f)(6))
ASK THE CREW
Which chemicals are on this location, and where are their safety data sheets?
From the talk: Oil and gas well site safety. Read it in full, free, with the questions and the sign-in sheet.