46 CFR § 162.028-2
Classification
April 15, 2021
(a) Portable and semi-portable extinguishers must be marked with a combined number and letter designation. The letter designates the general class of fire for which the extinguisher is suitable as identified in NFPA 10 (incorporated by reference, see §162.028-1). The number indicates the relative extinguishing potential of the device as rated by UL 711 (incorporated by reference, see §162.028-1).
(b) [Reserved]
[CGFR 60-36, 25 FR 10640, Nov. 5, 1960, as amended by USCG-2012-0196, 81 FR 48278, July 22, 2016]