A cleanroom is an environment where airborn particulates are controlled through an exchange of highly filtered air using a high efficiency particulate air (HEPA) filtering system, and through minimization of activities that generate particles.
A class 100 cleanroom maintains less than one hundred particles larger than 0.5 microns in each cubic foot of air space.
In addition to particle control, the cleanroom is temperature and humidity controlled to 70F, 45% RH.