Final answer:
Class D fire extinguishers should be inspected every 12 months and visually checked monthly to ensure their effectiveness in handling fires involving combustible metals.
Step-by-step explanation:
Class D fire extinguishers are specifically designed to handle fires involving combustible metals, such as magnesium, titanium, and sodium. These metals require a different type of extinguishing agent and a higher inspection frequency due to their unique characteristics and potential hazards.
According to the National Fire Protection Association (NFPA) guidelines, Class D extinguishers should be inspected at least every 12 months. This inspection should be performed by a qualified individual who checks for any signs of damage, corrosion, or leakage.
Additionally, NFPA recommends a more frequent visual inspection of Class D extinguishers on a monthly basis. During this inspection, the user should ensure that the extinguisher is easily accessible, the operating instructions are visible, and there are no obvious signs of tampering or obstruction.