Do you want to know more about cleanrooms？

2023-11-04

original

Marya

Cleanrooms maintain particulate free air by using HEPA or ULPA filters that use laminar or turbulent airflow principles. In order to minimize the carrying of particulate matter by people entering the clean room, staff enter and leave through air locks (sometimes including the air shower stage) and wear protective clothing such as headsets, masks, gloves, boots, and work clothes.

1.Air flow principle of cleanrooms

Cleanrooms maintain particulate free air by using HEPA or ULPA filters that use laminar or turbulent airflow principles. A laminar or unidirectional airflow system guides filtered air downwards or horizontally to a filter located on a wall near the clean room floor, or through an elevated perforated floor to be recirculated. Laminar airflow systems are typically used for 80% of clean room ceilings to maintain constant air handling. Stainless steel or other non shedding materials are used to construct laminar airflow filters and smoke hoods to prevent excess particles from entering the air. Turbulent or non unidirectional airflow uses laminar flow hoods and non-specific velocity filters to maintain constant movement of air in the clean room, although not all are in the same direction. Rough air attempts to capture particles that may exist in the air and push them towards the floor, where they enter the filter and leave the clean room environment. The US FDA and the European Union have established guidelines and restrictions on microbial contamination, which are very strict to ensure that there is no microbial contamination in pharmaceutical products. You can also use an inflatable chamber and adhesive pads between the air processor and fan filter unit.
In addition to air filters, cleanrooms can also use ultraviolet radiation to disinfect the air. UV devices can be installed in ceiling lighting fixtures and irradiate the air, killing potential infectious particles, including 99.99% of airborne microbial and fungal pollutants. Ultraviolet light has previously been used to clean surface pollutants in sterile environments, such as hospital operating rooms. As equipment becomes more affordable, their use in other clean rooms may increase. The potential advantages of UV based purification include reducing dependence on chemical disinfectants and extending the lifespan of HVAC filters.

2.Different types of cleanrooms

Some cleanrooms remain under positive pressure, so if any leakage occurs, air will leak out of the chamber instead of unfiltered air entering. This is most typical in semiconductor manufacturing, where even a small amount of particle leakage can contaminate the entire process, and any leakage will not be harmful to the surrounding community. The opposite is the case, for example, in high-level biological laboratories, dealing with contaminated viruses; They are always kept under negative pressure, and the exhaust gas passes through high-efficiency filters and further sterilization procedures. Both are still clean rooms, as the particle levels inside are kept within a very low range.
Some cleanroom HVAC systems control humidity at such low levels that additional equipment such as air ion generators are required to prevent electrostatic discharge issues. This is a particular concern in the semiconductor business, as electrostatic discharge can easily damage modern circuit designs. On the other hand, active ions in the air can also damage exposed components. Therefore, most workers in high electronic and semiconductor facilities must wear conductive shoes while working. Low level clean rooms may only require special shoes, with completely smooth soles that will not be contaminated with dust or dirt. However, for safety reasons, the sole of the shoe must not pose a risk of slipping. Entering a clean room is usually limited to individuals wearing clean room suits, including necessary machinery.
In clean rooms with less stringent air pollution standards, the entrance to the clean room may not have an air shower. The front hall (known as the "gray room") is used to put on clothes from the cleanroom. This practice is very common, for example in many nuclear power plants, which operate as a whole as a low-level backpressure clean room.

3.Recycling and Disposable Cleanrooms

The recirculation clean room returns air to the negative pressure chamber through low wall air reflux. Then, the air is pulled back to the cleanroom by the HEPA fan filter unit. The air is continuously recirculated and filtered through HEPA, removing particles from the air every time. Another advantage of this design is that it can be combined with air conditioning.
Once air is sucked in from outside the clean room through the clean room, it enters the clean room through the HEPA fan filtration unit. Then, the air flows through the exhaust grille to the outside of the clean room. The advantage of this method is its low cost. The disadvantage is that the HEPA fan filter has a short lifespan, lower particle count than similar recirculating clean rooms, and cannot accommodate air conditioning.

4.Operating Steps of cleanrooms

In order to minimize the carrying of particulate matter by people entering the clean room, staff enter and leave through air locks (sometimes including the air shower stage) and wear protective clothing such as headsets, masks, gloves, boots, and work clothes.
Common materials such as paper, pencils, and fabrics made of natural fibers are usually excluded, as they may shed particles during use.
The particle level is usually tested using a particle counter and microorganisms are detected and counted through environmental monitoring methods. The polymer tools used in the cleanroom must carefully determine their chemical compatibility with the cleanroom processing fluid and ensure the production of low levels of particles.
When cleaning, only use special mops and buckets. The cleaning chemicals used often involve sticky elements to capture dust, and may require the use of a light molecular weight solvent for the second step of removal. Clean room furniture is pre-designed to produce minimal particles and is easy to clean.

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