What does UL stand for in firestop testing?

The term UL in firestop testing stands for Underwriters Laboratories. This organization is a globally recognized, independent safety science company that develops standards and conducts testing for a wide variety of products, including firestop systems. Underwriters Laboratories focuses on ensuring that products meet specific safety and performance criteria, which is crucial in the context of firestop testing to prevent the spread of fire and smoke within buildings. Their rigorous testing protocols help manufacturers ensure that their firestop products will perform as intended in real-world situations.

The other terms do not accurately represent UL's identity. Underground Laboratories, for instance, does not exist in the context of firestop or building safety standards, while Universal Laboratories and United Laboratories are also not recognized entities in this particular field. Thus, Underwriters Laboratories is the correct association with firestop testing.