In the extinguisher rating 2-A:10-B:C, what does the C signify?

The letter C in the extinguisher rating 2-A:10-B:C specifically indicates that the extinguisher is suitable for use on energized electrical equipment. This designation is crucial because certain fire extinguishing agents can conduct electricity and pose additional hazards when used around live electrical components. Therefore, the C rating allows users to confidently apply the extinguisher to fires that involve electrical equipment without the risk of electric shock.

The extinguishing agents classified under this rating, such as dry chemical or CO2, are non-conductive and safe to use on live electrical fires, making the understanding of this rating vital for effective and safe firefighting. The presence of the C rating informs firefighters and users that this extinguisher meets industry standards for safety and effectiveness when dealing with electrical hazards.