This International Standard specifies two alternative methods for determining hygroscopic sorption properties of porous building materials and products: a) using desiccators and weighing cups (desiccator method); b) using a climatic chamber (climatic chamber method). The desiccator method is the reference method. This International Standard does not specify the method for sampling. The methods specified in this International Standard can be used to determine the moisture content of a sample in equilibrium with air at a specific temperature and humidity.