What is the highest level of health risk indicated in the NFPA 704 system?

In the NFPA 704 system, the highest level of health risk is indicated by a rating of 4. This numerical rating system uses a scale from 0 to 4, where each number corresponds to a level of hazard, with 0 indicating no risk and 4 representing a very high risk. A 4 rating denotes that exposure to the material could cause serious or lethal health effects, even with short-term exposure, making it critical for emergency responders to take extreme precautions when dealing with such materials. Understanding these ratings helps in assessing the potential dangers associated with hazardous substances and ensures proper safety measures are in place. The other options reflect lower levels of health risk, with 3 indicating serious health risks, 2 representing moderate risks, and 0 denoting no significant health risks.