Portable Fire Extinguisher Locations, NFC & NFPA 10 Each fire extinguisher has a label affixed to it. Annex G provides the following example to break down the rating on the label. "A fire extinguisher is rated and classified 4-A:20-B:C, which imparts the following information: it should extinguish approximately twice as much Class A fire as a 2-A rated fire extinguisher (2.5 gal (9.46 L)).