You're referring to the ISO 14644-1:2021 standard!
The ISO 14644-3:2019 standard (often referred to in its most recent update as part of the 2021 regulatory landscape) is a foundational document for the validation and performance testing of cleanrooms. Unlike Part 1, which focuses on classification, Part 3 specifies the actual used to ensure these controlled environments function correctly. iso 146443pdf 2021