What Is a Cleanroom?
Cleanrooms are specialized environments designed to control airborne particles, microorganisms, temperature, humidity, and pressure. They are essential in industries such as pharmaceuticals, biotechnology, electronics, and food processing, where even a tiny particle can compromise product quality or safety.
To ensure consistency across the world, cleanrooms are classified based on international standards that define how clean the air inside must be — measured by the number and size of particles present in a cubic meter of air.
Major Cleanroom Classification Standards
Cleanrooms are classified according to three main standards:
- ISO 14644-1 (International Standard)
- Federal Standard (FS) 209 (Older U.S. Standard, now replaced by ISO 14644-1)
- European Union GMP / WHO Guidelines
Relationship Between ISO, EU GMP, and FS Standards
| ISO Class | EU GMP / WHO Grade | FS 209 (Old Standard) |
|---|---|---|
| ISO 5 | Grade A | Class 100 |
| ISO 6 | Grade B | Class 1,000 |
| ISO 7 | Grade C | Class 10,000 |
| ISO 8 | Grade D | Class 100,000 |
ISO Classification Overview
According to ISO 14644-1, cleanrooms are categorized from ISO Class 1 (the cleanest) to ISO Class 9 (the least clean). In pharmaceutical and food environments, particle sizes of 0.5 micron and 5.0 micron are most relevant.
ISO Cleanroom Classes and Applications
ISO 5 – Grade A / Class 100
Description: The cleanest class used in pharmaceutical operations for the most critical manufacturing steps.
Particle Limits:
- ≤ 3,520 particles/m³ for particles ≥ 0.5 micron
- ≤ 29 particles/m³ for particles ≥ 5.0 micron
Air Changes per Hour (ACH): 240–480
Applications: Laminar Air Flow (LAF) units, product exposure and filling areas for injectables, sterile compounding zones.
ISO 6 – Grade B / Class 1,000
Description: A high level of cleanliness that supports ISO 5 or Grade A areas.
Particle Limits:
- ≤ 35,200 particles/m³ for particles ≥ 0.5 micron
- ≤ 290 particles/m³ for particles ≥ 5.0 micron
Air Changes per Hour (ACH): 150–240
Applications: Background areas for aseptic processing, material preparation and transfer rooms.
ISO 7 – Grade C / Class 10,000
Description: A clean environment suitable for less critical stages of manufacturing.
Particle Limits:
- ≤ 352,000 particles/m³ for particles ≥ 0.5 micron
- ≤ 2,960 particles/m³ for particles ≥ 5.0 micron
Air Changes per Hour (ACH): 60–90
Applications: Compounding and formulation rooms, non-sterile filling operations.
ISO 8 – Grade D / Class 100,000
Description: The least clean but still controlled environment, used for background or support activities.
Particle Limits:
- ≤ 3,520,000 particles/m³ for particles ≥ 0.5 micron
- ≤ 29,000 particles/m³ for particles ≥ 5.0 micron
Air Changes per Hour (ACH): 5–48 (typically around 20 in practice)
Applications: Packaging, labeling, and general support areas.
WHO / EU GMP Cleanroom Grades
| Grade | Description |
|---|---|
| Grade A | Highest cleanliness level for critical operations such as sterile product filling. |
| Grade B | Background environment for Grade A areas. |
| Grade C | Clean area for less critical stages such as solution preparation. |
| Grade D | Controlled area for handling components and general operations. |
Airborne Particulate Concentration (Schedule M & WHO)
| Grade | ISO Equivalent | At Rest (≥0.5µm) | At Rest (≥5.0µm) | In Operation (≥0.5µm) | In Operation (≥5.0µm) |
|---|---|---|---|---|---|
| A | ISO 4.8 | 3,520 | 20 | 3,520 | 20 |
| B | ISO 5 | 3,520 | 29 | 352,000 | 2,900 |
| C | ISO 7 | 352,000 | 29,000 | 3,520,000 | 29,000 |
| D | ISO 8 | 3,520,000 | 29,000 | Not defined | Not defined |
FS 209 Cleanroom Classification (Old System)
Before ISO 14644-1 was introduced, cleanrooms were categorized under FS 209E, which measured particles per cubic foot:
- Class 100
- Class 1,000
- Class 10,000
- Class 100,000
Although it has been replaced by ISO 14644-1, FS 209 terms are still commonly used for reference in many industries.
Summary Table
| ISO Class | Grade | FS Class | Particle Limit (≥0.5µm) | Particle Limit (≥5.0µm) | Air Changes/Hour | Typical Use |
|---|---|---|---|---|---|---|
| ISO 5 | Grade A | Class 100 | 3,520 | 29 | 240–480 | Sterile filling & LAF |
| ISO 6 | Grade B | Class 1,000 | 35,200 | 290 | 150–240 | Support to ISO 5 areas |
| ISO 7 | Grade C | Class 10,000 | 352,000 | 2,960 | 60–90 | Compounding & formulation |
| ISO 8 | Grade D | Class 100,000 | 3,520,000 | 29,000 | 5–48 | Background/packaging |
In Simple Terms
The lower the ISO number, the cleaner the air. Air Changes per Hour (ACH) indicates how often clean, filtered air replaces the room’s air each hour. Cleanrooms protect products and ensure regulatory compliance by maintaining environments free from contamination, vital for patient safety and product quality.