Semi-Quantitative Methods

The hazard diamond is used to identify and analyze the different risks associated with hazard sources. The hazard diamond or the so-called fire diamond is defined in the NFPA (704) which is the Standard System for the Identification of the Hazards of Materials for Emergency Response. The four divisions of the diamond are color-coded to represent flammability (red), health hazard (blue), chemical reactivity (yellow) and special hazards (white).The Hazard diamond is normally used to identify the risk associated with hazardous materials and dangerous goods.

The preliminary hazard analysis (PHA) is a semi-quantitative risk analysis methods that is used to identify potential hazards and the corresponding top events (risks). The PHA sheet identifies as well the required measures and follow-up actions to control the hazard sources. The PHA should consider hazardous components, facilities, safety-related equipment, and environmental constraints.

In a qualitative approach, risks are usually categorized into “high”, “medium” and “low”, and are represented in a risk matrix. This risk matrix represents the possibility and severity in order to integrate the potential accident scenarios that were identified in the threat identification stage. Inside the matrix, the criticality of a risk, through the use of colors, can identified. The results provided by this matrix can be used to compare risks and identify improvement and mitigation measures.