California Code of Regulations
Title 19 - Public Safety
Division 1 - State Fire Marshal
Chapter 3 - Fire Extinguishers
Article 23 - Table for Conversion of Classification of Older Extinguishers to Approximate Present Classification
Section 616.2 - Old Classification (Conversion)

Wherever fire extinguishers are found with the old classification on the label, use this table for approximate conversion and use the resulting classification value in applying Article 11 of this part. For example, a 15-pound carbon dioxide extinguisher has the classification "B-1, C-1" on the label. From this table, it is found that the approximate classification under the present method is "4-B,C" (--158).