In NFPA-10, fire extinguishers, when it says "2-A, 4-A, 5-B, 10B... etc. what does the numbers means?
According to NFPA10 - A rating number preceding the classification letter that indicates the relative extinguishing effectiveness. You can see Annex G - Extinguisher Classification and Rating System of this Code that explain this concept.
Francisco J. Martin
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