This situation happened at chemical factory. This case can happened anytime because I don’t see anything that indicates the time. So I can’t predict the time. The men in white shirt pour the chemical water in the tank. The tank with sign of chemical hazard and then the chemical react causing smoke that look dangerous and I saw two men dying behind the white shirt guy. So I think this case is very serious. You must be know for sure before you pour anything in the chemical tank. In this picture is not equipment involved but chemical water on the floor should be in the tank.