The classification relies on the formula relating the maximum allowable particles per cubic meter of air to the particle size. For example, an cleanroom is roughly equivalent to the old "Class 100" standard, meaning it allows no more than 3,520 particles per cubic meter that are 0.5 micrometers or larger.

: Outlines the requirements for monitoring and testing to provide evidence of continued compliance with air cleanliness.

: Its primary goal was to prevent ambiguity in contract negotiations between buyers and sellers and to ensure a unified language for scientists and engineers worldwide.