Annex 1 has long referenced ISO 14644-1 for cleanroom classification. Despite this, there were several differences in the defined limits between the two documents. The update to Annex 1 in 2022 removed these differences to achieve complete alignment. The result of this is that Annex 1 compliant classification testing can be achieved by selecting the appropriate ISO Class when using legacy AeroTrak Portable Particle Counters.