Which number on the NFPA Diamond denotes the highest level of hazard severity?

In the context of the NFPA (National Fire Protection Association) Diamond, the numbers on the diamond represent the severity of health, flammability, and reactivity hazards, with a range typically from 0 to 4. Each number signifies a different level of risk, with 0 indicating no hazard and 4 indicating the highest level of hazard severity.

Choosing 4 signifies that a substance poses a significant danger. For example, a rating of 4 in flammability means the material can ignite readily at room temperature and poses an extreme hazard. Thus, understanding the nuances of these ratings is essential in assessing hazards for proper safety measures and responses. The training and knowledge of these classifications are vital for safe handling and emergency procedures.