Troubles with the word "pure" Is it correct to use the word "pure" if you talk about an air cleaning filter? I've got one example here: "An overflow valve is arranged between the raw side and the pure side of the filter element and is displaced into an open position in case the pressure of the liquid exceeds a threshold value on the raw side of the filter element." (www.wipo.int) And would it be correct to use the word "pure" to say that a room, e.g. a clean room in the pharmceutical field, is free of germs and other microorganisms? An example: When you open a transfer hatch in a clean room, you open it on the pure side of the transfer hatch. Please help me to understand the usage of the word "pure" correctly. Thank you. P.S. Yes, I know, that "pure" is usually used in the chemistry (pure water, pure gold, etc.) but as I see people use it in different areas in different ways.