What is a Cleanroom? Cleanroom Classifications, Class 1, 10, 100, 1,000, 10,000, 100,000, ISO Standard 14644, Cleanroom Definition

Depending on the room classification or function, personnel gowning may be as limited as lab coats and hairnets, or as extensive as fully enveloped in multiple layered bunny suits with self contained breathing apparatus.

Cleanroom clothing is used to prevent substances from being released off the wearer's body and contaminating the environment. The cleanroom clothing itself must not release particles or fibers to prevent contamination of the environment by personnel. This type of personnel contamination can degrade product performance in the semiconductor and pharmaceutical industries and it can cause cross-infection between medical staff and patients in the healthcare industry for example.

Cleanroom garments include boots, shoes, aprons, beard covers, bouffant caps, coveralls, face masks, frocks/lab coats, gowns, glove and finger cots, hairnets, hoods, sleeves and shoe covers. The type of cleanroom garments used should reflect the cleanroom and product specifications. Low-level cleanrooms may only require special shoes having completely smooth soles that do not track in dust or dirt. However, shoe bottoms must not create slipping hazards since safety always takes precedence. A cleanroom suit is usually required for entering a cleanroom. Class 10,000 cleanrooms may use simple smocks, head covers, and booties. For Class 10 cleanrooms, careful gown wearing procedures with a zipped cover all, boots, gloves and complete respirator enclosure are required.

Cleanroom Air Flow Principles

Cleanrooms maintain particulate-free air through the use of either HEPA or ULPA filters employing laminar or turbulent air flow principles. Laminar, or unidirectional, air flow systems direct filtered air downward in a constant stream. Laminar air flow systems are typically employed across 100% of the ceiling to maintain constant, unidirectional flow. Laminar flow criteria is generally stated in portable work stations (LF hoods), and is mandated in ISO-1 through ISO-4 classified cleanrooms.

Proper cleanroom design encompasses the entire air distribution system, including provisions for adequate, downstream air returns. In vertical flow rooms, this means the use of low wall air returns around the perimeter of the zone. In horizontal flow applications, it requires the use of air returns at the downstream boundary of the process. The use of ceiling mounted air returns is contradictory to proper cleanroom system design.

Cleanroom Classifications

Cleanrooms are classified by how clean the air is. In Federal Standard 209 (A to D) of the USA, the number of particles equal to and greater than 0.5µm is measured in one cubic foot of air, and this count is used to classify the cleanroom. This metric nomenclature is also accepted in the most recent 209E version of the Standard. Federal Standard 209E is used domestically. The newer standard is TC 209 from the International Standards Organization. Both standards classify a cleanroom by the number of particles found in the laboratory's air. The cleanroom classification standards FS 209E and ISO 14644-1 require specific particle count measurements and calculations to classify the cleanliness level of a cleanroom or clean area. In the UK, British Standard 5295 is used to classify cleanrooms. This standard is about to be superseded by BS EN ISO 14644-1.

Cleanrooms are classified according to the number and size of particles permitted per volume of air. Large numbers like "class 100" or "class 1000" refer to FED_STD-209E, and denote the number of particles of size 0.5 µm or larger permitted per cubic foot of air. The standard also allows interpolation, so it is possible to describe e.g. "class 2000."

Small numbers refer to ISO 14644-1 standards, which specify the decimal logarithm of the number of particles 0.1 µm or larger permitted per cubic metre of air. So, for example, an ISO class 5 cleanroom has at most 105 = 100,000 particles per m³.

Both FS 209E and ISO 14644-1 assume log-log relationships between particle size and particle concentration. For that reason, there is no such thing as zero particle concentration. Ordinary room air is approximately class 1,000,000 or ISO 9.

ISO 14644-1 Cleanroom Standards

Class maximum particles/m3 FED STD 209E
equivalent >=0.1 µm >=0.2 µm >=0.3 µm >=0.5 µm >=1 µm >=5 µm ISO 1 10 2           ISO 2 100 24 10 4       ISO 3 1,000 237 102 35 8   Class 1 ISO 4 10,000 2,370 1,020 352 83   Class 10 ISO 5 100,000 23,700 10,200 3,520 832 29 Class 100 ISO 6 1,000,000 237,000 102,000 35,200 8,320 293 Class 1,000 ISO 7       352,000 83,200 2,930 Class 10,000 ISO 8       3,520,000 832,000 29,300 Class 100,000 ISO 9       35,200,000 8,320,000 293,000 Room Air

BS 5295 Cleanroom Standards

  maximum particles/m3 Class >=0.5 µm >=1 µm >=5 µm >=10 µm >=25 µm Class 1 3,000   0 0 0 Class 2 300,000   2,000 30   Class 3   1,000,000 20,000 4,000 300 Class 4     20,000 40,000 4,000