TPP (Thermal Protective Performance)
The TPP test measures the elapsed time for heat emitted from a radiant and convective heat source to go through all layers of a composite system (Outer shell – Moisture barrier – Thermal barrier) and resulting in a second-degree burn, as it may occur in a flash over situation. The higher the TPP value, the better the thermal protection. The TPP value has an inverse effect on the THL value. A higher TPP value is generally obtained with a thicker thermal barrier. A difference in TPP value between two different composite of less than 2 is not generally considered to be physically perceivable by a firefighter.