Part 8 of ISO 14644 covers the classification of airborne molecular contamination (AMC) in cleanrooms and associated controlled environments. The standard addresses AMC in terms of airborne concentrations of specific chemical substances, individual, group or category. Four classes of compound are defined: acids, bases, organic and inorganic and five categories of contaminant: biotoxics, condensables, corrosives, dopants and oxidants. The standard provides a protocol to include test methods, analysis and time weighted factors within the specification for classification of AMC and currently considers only concentrations of AMC between 100 and 10-12 g/m3 under cleanroom operational conditions.