A "porous surface" refers to a material or object that has tiny holes or spaces within it. These holes allow liquids or gases to pass through or soak into the surface easily. Full definition
This is because some viruses, including canine and feline parvovirus, have the ability to survive for months and are relatively resistant to cleaning and disinfection, especially when they are deposited on porous surfaces such as carpet, grass, or wood. (animalsheltering.org)
They now have to live in a kennel building on concrete and are not allowed porous surfaces of any kind - that means no beds, no blankets, not even a towel to lay on. (dogingtonpost.com)
Naomi's Nucleants are made from bio-glass material (CaO - P2O5 - SiO2) and has a highly porous surface with cavities of similar sizes to proteins (see image right). (moleculardimensions.com)