Cleanroom Overview and Classifications
Cleanrooms are typically used in scientific research and manufacturing to provide a controlled environment for handling sensitive components and samples. Depending on your specific standards, they can allow for varying levels of contaminants, such as airborne microbes, dust, particles, and chemical vapors, that are measured by the number of particles per cubic meter. Often containments are kept at low levels since they can greatly affect the application and component. Cleanrooms are widely used in biotechnology, electronic assembly, semiconductor manufacturing, pharmaceutical, medical, industrial and applications that are highly sensitive to environmental contamination. For example, controlled environments are used in semiconductor manufacturing and pharmaceutical production since containments can degrade the product’s performance. In the health care industry, personnel or airborne contamination can cause cross-infection between medical staff and patients.
Cleanroom Overview
The main objective of a cleanroom is to maintain a constant environment with controlled levels of airborne particles. This can be achieved by preventing particles and airborne contaminants from entering the enclosed environment. Any external air entering the environment needs to be filtered through a HEPA or ULPA filter and in some cases, clean rooms can be kept at a positive pressure so that unfiltered air does not leak into the filtered environment.
Additionally, the internal air needs to be constantly recirculated through filters to remove particles produced within the enclosed environment. The unidirectional laminar air flow system directs a constant stream of filtered air into the controlled environment and keeps the internal air moving. The multi-directional air movement traps the particles in the cleanroom by driving them towards the floor, where they enter the air flow system and are filtered out the air supply.
Second, particle pass-through from personnel and equipment to the environment can be limited using an intermediate airlock, cleanroom-safe equipment/furniture, and cleanroom clothing. The easiest measure is to use equipment that is easy to clean and are designed to produce minimal air contamination.
Individuals entering or leaving the cleanroom to go through an antechamber that is referred to as an airlock or an anteroom. Depending on the contamination standards, the chamber may include an air shower to remove containments from personnel or object surfaces before entering the anteroom. In this chamber, personnel will put on a special suit or a range of cleanroom clothing to allow them to enter the cleanroom environment.
Individuals entering or leaving the cleanroom to go through an antechamber that is referred to as an airlock or an anteroom. Depending on the contamination standards, the chamber may include an air shower to remove containments from personnel or object surfaces before entering the anteroom. In this chamber, personnel will put on a special suit or a range of cleanroom clothing to allow them to enter the cleanroom environment.
Cleanroom Classifications
Cleanrooms are classified according to how clean the air is based on the number of 0.5 mm or larger particles per cubic feet or meters. According to US Federal Standard 209 (A through D), they are classified according to the number and size of particles that are permitted per volume of air. For example, class 100 denotes the number of particles that are 0.5 mm or larger per cubic foot of air. The following is a table shows the various cleanroom classifications based on US Federal Standards:
| Class |
Maximum particles/ft3 |
ISO equivalent |
| ≥0.1 µm |
≥0.2 µm |
≥0.3 µm |
≥0.5 µm |
≥5 µm |
|
| 1 |
35 |
7.5 |
3 |
1 |
0.007 |
ISO 3 |
| 10 |
350 |
75 |
30 |
10 |
0.07 |
ISO 4 |
| 100 |
3,500 |
750 |
300 |
100 |
0.7 |
ISO 5 |
| 1,000 |
35,000 |
7,500 |
3,000 |
1,000 |
7 |
ISO 6 |
| 10,000 |
350,000 |
75,000 |
30,000 |
10,000 |
70 |
ISO 7 |
| 100,000 |
3.5×106 |
750,000 |
300,000 |
100,000 |
830 |
ISO 8 |
The US federal standards were officially canceled in November 2001, with most switching to ISO-14644-1 and ISO 14698 standards that measure the number and size of particles that are permitted per cubic meter of air. The following is the table:
| Class |
Maximum particles/m3 a |
FED STD 209E equivalent |
| ≥0.1 µm |
≥0.2 µm |
≥0.3 µm |
≥0.5 µm |
≥1 µm |
≥5 µm |
|
| ISO 1 |
10b |
d |
d |
d |
d |
d |
|
| ISO 2 |
100 |
24b |
10b |
d |
d |
e |
|
| ISO 3 |
1,000 |
237 |
102 |
35b |
d |
e |
Class 1 |
| ISO 4 |
10,000 |
2,370 |
1,020 |
352 |
83b |
e |
Class 10 |
| ISO 5 |
100,000 |
23,700 |
10,200 |
3,520 |
832 |
d,e,f |
Class 100 |
