A hazardous area is defined as a three-dimensional space in which a flammable atmosphere may be expected to be present at such frequencies as to require special precautions for the control of potential ignition sources including fixed electrical equipment.
EI15, API505 and NFPA497 provides an overview of the process of hazardous area classification.
There are various approaches to establish hazardous zones i.e. direct example method, point source method and risk-based method.
The point source methodology involves the following steps:
- Identify point sources and associated release conditions;
- Determine grade of release;
- Determine fluid category;
- Establish zone classification;
- Determine hazard radii;
Hazardous area classification drawing outlines the classifications of areas where flammable liquids, gasses or vapors are handed, processed or stored. It is created based on input from the Process Flow Diagrams, Piping & Instrumentation Diagrams and the Equipment Location Plan.
The intent of the drawing is to communicate to engineers, operators and contractors information on the hazardous material that may be present and the probability that it is in the atmosphere. This knowledge allows for engineers and designers to select the right equipment and for contractors to know how to properly install the equipment.