Clean Room
As the name would suggest, the purpose of a clean room is to be clean, and therefore free of any contaminants or pollutants. This is useful in scientific experiment particularly where a tiny difference in atmospheric makeup could affect the results of the experiment. There are different levels of cleanroom which require different levels of ppe to enter, lower level cleanrooms may only require a smock, a hood and some boots to enter but the highest-level cleanroom would require a full coverall and respirator to enter.