What is the minimum required back-up supply of extinguishing agent for metal fires?

For metal fires, the minimum required back-up supply of extinguishing agent is set at 150%. This means that when calculating the amount of extinguishing agent needed to effectively combat a metal fire, it is essential to have an additional 50% on top of the calculated amount. The reason for this increased supply requirement is due to the unpredictability and difficulty associated with extinguishing metal fires, particularly because not all extinguishing agents are effective on all types of metal.

Having a backup supply ensures that in the event of complications, such as the fire spreading or not being extinguished on the first attempt, the instructor will have enough agent readily available to manage the situation effectively. This approach also accounts for any losses that might occur during the extinguishing process or miscalculations in the initial assessment of the fire's intensity. Thus, a safety margin is crucial in fire suppression tactics, especially in high-risk scenarios involving combustible metals.