Clean room standardization

In the United States, until the end of November 2001, federal standard 209E (FED-STD-209E) was used to define requirements for clean rooms. On November 29, 2001, these standards were replaced by the publication of ISO Specification 14644-1. Typically, a clean room used for manufacturing or scientific research is a controlled environment with low levels of contaminants, such as dust, airborne microbes, aerosol particles, and chemical vapors. To be precise, the cleanroom has a controlled pollution level, which is specified by the number of particles per cubic meter at a specified particle size. In a typical urban environment, outdoor air contains 35 million particles per cubic meter, 0.5 microns in diameter or larger, corresponding to an ISO 9 clean room at the lowest level of the clean room standard. Clean rooms are classified according to the cleanliness of the air. In U.S. Federal Standard 209 (A through D), the number of particles equal to or greater than 0.5mm is measured in 1 cubic foot of air, and this count is used to classify clean rooms. This metric nomenclature is also accepted by the latest 209E version of the standard. China uses federal standard 209E. The newer standard is the International Standards Organization's TC 209. Both standards classify clean rooms based on the number of particles in the laboratory air. The clean room classification standards FS 209E and ISO 14644-1 require specific particle count measurements and calculations to classify the cleanliness level of a clean room or clean area. In the United Kingdom, British Standard 5295 is used to classify clean rooms. This standard will soon be replaced by BS EN ISO 14644-1. Clean rooms are classified according to the number and size of particles allowed per volume of air. Large numbers like "Class 100" or "Class 1000" refer to FED_STD209E, representing the number of particles of 0.5 mm or larger size allowed per cubic foot of air.