Which number set would indicate the most dangerous chemical on an NFPA 704 placard?

Which number set would indicate the most dangerous chemical on an NFPA 704 placard?

• A. 3, 2, 1
• B. 0, 2, 4
• C. 4, 4, 2
• D. 3, 3, 2

Answer: (C)

NFPA 704 ratings show hazard in three areas—health, flammability, and reactivity—each on a scale from zero to four, with higher numbers meaning greater danger. To figure out the most dangerous chemical, focus on the two categories that describe immediate harm if exposed or ignited: health and flammability. The combination that pairs the maximum health hazard with the maximum flammability hazard represents the strongest overall danger, especially when reactivity is not at its highest but remains at a moderate level. The other sets have at least one of those two top hazards lower, or include a zero in health, which reduces overall danger. So the set with the highest health and flammability ratings, plus a mid-level reactivity rating, indicates the most dangerous chemical.

NFPA 704 ratings show hazard in three areas—health, flammability, and reactivity—each on a scale from zero to four, with higher numbers meaning greater danger. To figure out the most dangerous chemical, focus on the two categories that describe immediate harm if exposed or ignited: health and flammability. The combination that pairs the maximum health hazard with the maximum flammability hazard represents the strongest overall danger, especially when reactivity is not at its highest but remains at a moderate level. The other sets have at least one of those two top hazards lower, or include a zero in health, which reduces overall danger. So the set with the highest health and flammability ratings, plus a mid-level reactivity rating, indicates the most dangerous chemical.