ISO 12571:2013 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. ISO 12571:2013 does not specify the method for sampling. The methods specified in ISO 12571:2013 can be used to determine the moisture content of a sample in equilibrium with air at a specific temperature and humidity.