What is the minimum requirement for a periodic inspection of class D extinguishing agents?

The minimum requirement for a periodic inspection of class D extinguishing agents is the verification of fullness by weighing or hefting. This method is crucial because class D extinguishing agents are designed for specific types of fires involving combustible metals, which necessitate ensuring the agent is available and effective in an emergency. By weighing or hefting the extinguisher, the technician can effectively determine if the agent is still present and has not been compromised or used.

While other options may be important in maintaining the overall effectiveness of the extinguisher, they do not constitute the minimum inspection requirement specified for class D agents. Options such as annual inspections, checking for label wear, or conducting monthly visual inspections may serve different purposes or apply to other classes of extinguishers, but they do not replace the necessity of confirming the agent's fullness specifically for class D extinguishers. This focus on agent verification highlights the critical aspect of readiness and reliability in fire safety equipment.