The Product Quality Research Institute (PQRI) defines a HAZOP as a way of identifying potential hazards in a system, and identifying operability problems likely to lead to nonconforming products. They lay out an approach to performing a HAZOP on the system design, physical and operational environment, and on operational and procedural controls.

You can read the PQRI tutorial on performing HAZOPs at the following link: http://pqri.org/wp-content/uploads/2015/08/pdf/HAZOP_Training_Guide.pdf.