What Is a Cleanroom?
A cleanroom is a room in which the concentration of airborne particles is controlled and classified, and which is designed, constructed and operated to control the introduction, generation and retention of particles inside the room. Other environmental parameters such as temperature, humidity and pressure are also controlled where required. These rooms are designed to protect product quality and worker health.
A cleanroom is not, by itself, a sterile environment. An ISO 14644-1 class defines only the airborne particle concentration; it does not assess whether the particles are viable. Applications such as sterile product manufacturing additionally require microbiological monitoring and the relevant GMP requirements, such as EU GMP Annex 1.
On What Basis Are Cleanrooms Classified?
Today, cleanroom classes are determined according to the international standard ISO 14644-1. Older class names that are still encountered in the industry come from the former US standard FED STD 209E:
- ISO 14644-1: The most widely used international standard.
- FED STD 209E: The former US federal standard, cancelled on 29 November 2001 and superseded by ISO 14644-1 and ISO 14644-2. Older class names such as "Class 100" are still used informally in the industry; Class 100 corresponds approximately to ISO 5.
Cleanroom Classifications According to ISO 14644-1
According to the ISO standard, cleanrooms are classified between ISO 1 (cleanest) and ISO 9 (least clean) based on the number of airborne particles between 0.1 and 5 microns.
The values in the table are based on ISO 14644-1:2015, Table 1, and show the maximum permitted cumulative concentration of particles equal to or larger than the stated size, per cubic metre of air (particles/m³).
| Class | ≥0.1 µm Particles/m³ | ≥0.5 µm Particles/m³ | Example applications (project requirements may vary) |
|---|---|---|---|
| ISO 1 | 10 | Not specified* | Highly specialised processes; requirements are defined per process |
| ISO 5 | 100,000 | 3,520 | Sterile manufacturing: Grade A zones (e.g. aseptic filling) and Grade B at rest |
| ISO 7 | Not specified** | 352,000 | Sterile manufacturing: Grade B in operation and Grade C at rest |
| ISO 8 | Not specified** | 3,520,000 | Sterile manufacturing: Grade C in operation and Grade D at rest |
* No limit is specified for ISO Class 1 at ≥0.5 µm; at such low concentrations, sampling and statistical limitations make classification at this size inappropriate.
** No limit is specified for ISO Classes 7 and 8 at ≥0.1 µm; concentration limits are not applicable in this region because of the very high particle concentration. These classes are classified at ≥0.5 µm, ≥1 µm and ≥5 µm.
The example applications are indicative only; the required class for each project is determined by the process and a risk assessment. The EU GMP grade correspondences are based on the ≥0.5 µm total particle limits in EU GMP Annex 1, Table 1, and do not cover the microbiological limits.
✅ Note: An ISO 5 class cleanroom is generally supported by laminar air flow systems.
How Is a Cleanroom Class Selected?
The following criteria are taken into account when selecting a cleanroom class:
- The sensitivity of the product to be manufactured
- Legal regulations
- Industry standards
- Worker safety and product sterility
Which Industry Uses Which Class?
🔬 Pharmaceutical Industry
In sterile pharmaceutical manufacturing, clean areas are defined by the EU GMP Annex 1 grades A, B, C and D. Critical operations such as filling take place in a Grade A zone, with Grade B as its background. Based on the ≥0.5 µm total particle limits in Annex 1, Table 1, Grade A corresponds to ISO 5 both at rest and in operation; Grade B to ISO 5 at rest and ISO 7 in operation; Grade C to ISO 7 at rest and ISO 8 in operation; and Grade D to ISO 8 at rest, with in-operation limits set by the manufacturer on the basis of a risk assessment. These correspondences cover total particle limits only; GMP grades also include microbiological limits. For non-sterile manufacturing, the required class is determined by product and process risk.
🧬 Biotechnology and Laboratories
In GMP applications such as cell and gene therapy products, classes are determined by the EU GMP grades and a risk assessment. In research laboratories, the required class depends on the work performed; no single ISO range applies to all applications.
💻 Electronics and Microchip Manufacturing
In semiconductor manufacturing, the required class depends on the process step; the most critical steps, such as lithography, are performed in the cleanest areas of the facility, and wafers are mostly transported in enclosed mini-environments such as FOUPs.
The Importance of Cleanroom Classifications
Correctly determining and applying cleanroom classifications;
- Increases product safety.
- Minimizes the risk of contamination.
- Ensures legal compliance.
- Reduces costs in the long term.
Conclusion: Maximum Efficiency with the Right Cleanroom Class
Cleanroom classifications are a critical factor that directly affects the quality and safety of production environments. Regardless of the industry, selecting the appropriate class is of great importance for both production success and legal compliance.