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Definition and standard of clean room

Popularity:1 Release time:2022-06-02 17:49:48

Clean rooms are used in almost every industry where small particles can adversely affect the manufacturing process. They vary in size and complexity and are widely used in industries such as semiconductor manufacturing, pharmaceuticals, biotechnology, medical devices and life sciences, as well as critical process manufacturing common to aerospace, optics, military and energy.

Definition and standard of clean room

Overview of clean room

A clean room is any given containment space specified to reduce particulate contamination and control other environmental parameters such as temperature, humidity, and pressure. The key component is a high-efficiency particulate air (HEPA) filter designed to capture particles of 0.3 microns and larger. All air delivered to the clean room passes through HEPA filters and, in some cases where strict cleaning performance is required, ultra-low particulate air (ULPA) filters are used.

Personnel selected to work in clean rooms receive extensive training in pollution control theory. They enter and leave the clean room through airlocks, air showers and/or changing rooms, and they must wear special clothing to capture the pollutants naturally produced by the skin and body.

Depending on the classification or function of the room, personnel clothing may be as limited as lab coats and hair nets, or completely wrapped in a multi-layer rabbit suit with self-contained breathing apparatus.

Cleanroom clothing is used to prevent substances from falling off the wearer's body and contaminating the environment. Clean room clothing itself should not release particles or fibers, in order to prevent people from polluting the environment. This type of human contamination can degrade product performance in the semiconductor and pharmaceutical industries and, for example, can lead to cross-infection between medical workers and patients in the healthcare industry.

Clean room clothing

Cleanroom clothing includes boots, shoes, aprons, beard covers, puffy hats, work clothes, face masks, dresses/lab coats, gowns, gloves and finger covers, hair nets, head covers, sleeves and shoe covers. The type of cleanroom clothing used should reflect the cleanroom and product specifications. Low level cleanrooms may only require special shoes with completely smooth soles that don't track dust or dirt. However, the sole must not create a slip hazard as safety is always a priority. Cleanroom clothing is usually required to enter a clean room. Class 10,000 cleanrooms can use simple smocks, hoods and ankle boots. For class 10 cleanrooms, careful robe wearing procedures are required and come complete with zip cover, boots, gloves and full respirator housing.

Two, the principle of clean room air flow

Clean rooms maintain particle-free air by using HEPA or ULPA filters based on laminar or turbulent flow principles. Laminar or unidirectional flow systems direct filtered air downward at a constant flow rate. Laminar airflow systems are usually used on 100% of the ceiling to maintain a constant one-way flow. Laminar flow standards are usually stated in portable workstations (LF hoods) and are mandatory in ISO-1 to ISO-4 classified cleanrooms.

Proper clean room design includes the entire air distribution system, including adequate downstream air recovery. In a vertical flow chamber, this means using low-wall air return around the perimeter of the area. In horizontal flow applications, it requires the use of air return at the downstream boundary of the process. Air return using a ceiling installation is inconsistent with an appropriate clean room system design.

Three, clean room classification

Clean rooms are classified according to air cleanliness. In the United States federal standards 209 (A through D), particles equal to or greater than 0.5mm are measured in one cubic foot of air, and this count is used to classify clean rooms. The latest 209E version of the standard also accepts the metric. Federal standard 209E is used domestically. A more recent standard is TC 209 of the International Standards Organization. Both standards classify clean rooms based on the number of particles in the laboratory air. Cleanroom classification standards FS 209E and ISO 14 ** 4-1 require specific particle count measurements and calculations to classify cleanliness levels in a cleanroom or clean area. In the United Kingdom, British Standard 5295 is used to classify clean rooms. This standard is to be replaced by BS EN ISO 14 ** 4-1.

Clean rooms are classified according to the number and size of particles allowed per unit of air. Large numbers such as "level 100" or "level 1000" refer to FED_STD-209E and indicate the number of particles of 0.5mm or larger allowed per cubic foot of air. The standard also allows interpolation, so it can be described for example as "Class 2000".

The small number refers to the ISO 14 ** 4-1 standard, which specifies the decimal logarithm of the number of particles 0.1 micron or larger allowed per cubic meter of air. Thus, for example, an ISO class 5 cleanroom has a maximum of 105 = 100,000 particles per m.

Both FS 209E and ISO 14 ** 4-1 assume a log-log relationship between particle size and particle concentration. So there is no such thing as zero particle concentration. Ordinary indoor air is approximately 1,000,000 or ISO 9.

Iv. ISO 14 ** 4-1 clean room standard

Five, BS 5295 clean room standard

The above is about the definition of clean room, and the classification and principle of purification workshop can be understood here.

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