ISO Certified Laboratory
An ISO Laboratory is a type of production facility you might see mentioned on some e-liquid bottles. ISO certification means that the cleanroom used in the production of a product has undergone testing and meets the foreign particle concentration levels for a given ISO class, shown below:
The lower the ISO class number a company seeks to attain for a given cleanroom, the harder and more costly it is to build said room. Generally, the lower the number, the more controlled (and clean) the environment inside the room. ISO 7 and lower are generally considered the standard for e-liquid production, although many e-liquids worldwide are not produced in certified cleanrooms.