本文件规定了通过扩散测定试样长期吸水率的设备和程序。适用于隔热产品。其目的是模拟产品在高相对湿度下的吸水率，两侧的相对湿度约为100%，并在长时间内承受水蒸汽压力梯度，例如倒置的屋顶或无保护的地面隔热层。 本试验不适用于所有类型的隔热产品。相关产品标准应说明本试验适用于哪些产品（如有）。

This document specifies the equipment and procedures for determining the long-term water absorption of test specimens by diffusion. It is applicable to thermal insulating products. It is intended to simulate the water absorption of products subjected to high relative humidities, approximating to 100 %, on both sides and subjected to a water vapour pressure gradient for a long period of time e.g. inverted roof or unprotected ground insulation. The test is not applicable for all types of thermal insulating products. The relevant product standard should state for which of its products, if any, this test is applicable.