Ultrafine particles (UFP)

According to the most common definitions, ultrafine particles (UFP) or ultrafine dust refer to airborne particles with a diameter of between 1 and 100 nanometres (nm) (DIN 2006; ISO 2007; VDI 2009; EPA 2004). UFPs represent the ultrafine sub-fraction of fine particles, the latter of which usually refer to the size range < 1 micrometre, i.e. 1,000 nm. In common usage, UFPs are particles in the range < 100 nm that are generated unintentionally by humans or occur naturally in the ⁠atmosphere⁠.