Under what condition must containers involved in a fire be permanently removed from service?

Containers made from aluminum or composite materials must be permanently removed from service if they have been involved in a fire due to the unique properties of these materials. Aluminum, while durable, can lose structural integrity when subjected to high temperatures, which compromises its ability to safely hold propane gas. Similarly, composite materials, often made from a combination of fibers and resins, can degrade or develop damage when exposed to extreme heat, leading to potential leaks or failures.

In a fire situation, the thermal characteristics of aluminum and composite materials can lead to immediate safety hazards. Once exposed to fire, these containers can become unreliable for safe transport and storage of propane. As a result, industry standards dictate that they should always be replaced to prevent any risk of explosion or leak in the future.

Other materials, like steel, paper, or plastic, have different considerations; for instance, steel containers, while affected by fire, might not necessarily require immediate removal if they do not show significant deformation or damage. Paper and plastic, on the other hand, would typically not be used for propane storage due to their highly flammable nature in the first place, rendering them ineffective options for safe propane containment.