What does the shaded background symbol with a slash indicate regarding fire extinguishers?

The shaded background symbol with a slash is a universal indication that the fire extinguisher must not be used in certain conditions or circumstances. This symbol typically warns users that using the extinguisher in those scenarios could be dangerous or ineffective, possibly due to the nature of the fire or the materials involved.

For example, if the extinguisher is not suitable for flammable metals or electrical fires, the symbol would advise against its use in such situations. Understanding this symbol is crucial for ensuring safety and effective fire response, as using an inappropriate extinguisher can exacerbate a fire or lead to further hazards. This highlights the importance of being aware of the specific classifications and limitations of each extinguisher type on a site.