Porous materials are classified into several kinds by their size. According to IUPAC notation (see J. Rouquerol et al., Pure & Appl. Chem, 66 (1994) 1739-1758), microporous materials have pore diameters of less than 2 nm, mesoporous materials have pore diameters between 2 nm and 50 nm and macroporous materials have pore diameters of greater than 50 nm.
Microporous materials are often used in laboratory environments to facilitate contaminant-free exchange of gases. Mold spores, bacteria, and other airborne contaminants will become trapped, while allowing gases to pass through the material. This allows for a sterile environment in the contained area.
Microporous materials may also be used in first aid, commonly operating under the tradename Micropore. Micropore can be used to affix dressings to wounds, and to hold bandages in place. If necessary it can be used to cover small wounds with gauze padding, usually as a temporary measure until a proper dressing and bandage are available.