The conditioning prescribed in this recommended practice is designed to obtain reproducible test results on thermal insulating materials. Results of tests obtained on these materials under uncontrolled atmospheric conditions may not be comparable with each other. Some of the physical properties of thermal insulating materials are influenced by relative humidity and temperature in a manner that affects the results of tests. In order that reliable comparisons may be made among different materials and products, and between different laboratories, it is necessary to standardize the humidity and temperature conditions to which insulating materials are subjected prior to and during testing.

Note 1-In some cases (for example, dimensionally unstable materials), the dry mass cannot easily be established and original mass has to be used.

It may be important to the user of thermal insulation to know physical properties (influenced by humidity) at the ambient conditions of use, as well as at standard conditions customarily specified for testing. In such instances, those special ambient conditions should be stated in the pertinent material specifications and test methods.