Understanding cleanroom classes: ISO 14644-1 and GMP Grades A to D
Anyone choosing cleanroom garments meets two class systems: the ISO classes of ISO 14644-1 and the GMP Grades A to D from EU GMP Annex 1. This guide explains both systems, shows how they relate and derives which garments are usual in which class. It is written for purchasing, quality assurance and production management.
At a glance
- ISO 14644-1 ranks cleanrooms by the number of particles per cubic metre of air; the smaller the number, the cleaner the air.
- GMP Grades A to D add requirements for sterile manufacturing at rest and in operation.
- The class describes the air, not the garment; which garments are prescribed is set by the operation's contamination control strategy.
- For GMP A/B sterile, individually packed garments are usual; for C/D non-sterile garments with hair and beard covers.
- Related products: garment kits, coveralls and frocks.
ISO classes to ISO 14644-1
ISO 14644-1 classifies cleanrooms by the maximum permitted number of airborne particles per cubic metre. The classes run from ISO 1 to ISO 9; each step allows ten times more particles than the previous one. Measurement uses particle counters at defined sampling points whose number depends on the room area. The table shows the limits for particles of at least 0.5 µm.
| ISO class | Particles ≥ 0.5 µm per m³ | Typical use |
|---|---|---|
| ISO 4 | 352 | Semiconductor manufacturing, optics |
| ISO 5 | 3,520 | Aseptic filling, GMP A and B at rest |
| ISO 6 | 35,200 | Medical devices, microelectronics |
| ISO 7 | 352,000 | GMP B in operation, GMP C at rest |
| ISO 8 | 3,520,000 | GMP C in operation, GMP D at rest, ante-rooms |
| ISO 9 | 35,200,000 | Normal room air |
The standard defines further particle sizes from 0.1 to 5 µm; the operator chooses the sizes relevant to the process. For ISO 5 and better, counting large particles from 5 µm is no longer used as a classification criterion in the current edition because the statistics become unreliable at low concentrations. Please check the values against the current edition of the standard.
GMP Grades A to D
The EU GMP guide regulates the manufacture of medicinal products. Its Annex 1 describes the manufacture of sterile products and divides cleanroom areas into Grades A to D. Unlike the ISO classes it distinguishes between the at-rest state (equipment running, no personnel) and operation (personnel working). Grade A is the critical zone where open product is handled, for example under laminar flow or in an isolator. Grade B is the background to Grade A; Grades C and D are less critical areas for preparatory steps.
| GMP grade | ≥ 0.5 µm per m³, at rest | ≥ 0.5 µm per m³, in operation | Corresponds roughly to |
|---|---|---|---|
| A | 3,520 | 3,520 | ISO 5 at rest and in operation |
| B | 3,520 | 352,000 | ISO 5 at rest, ISO 7 in operation |
| C | 352,000 | 3,520,000 | ISO 7 at rest, ISO 8 in operation |
| D | 3,520,000 | not defined | ISO 8 at rest |
In addition to particle limits, the GMP grades apply microbiological limits, for example for airborne microbes, settle plates and glove prints. These limits are the reason garments in Grades A and B must be sterile: the person is the most important source of microbes in the cleanroom.
What the class means for garments
The class describes the air, not the garment. A manufacturer can state which classes an article is designed or documented for; whether it may be used in your room is decided by your contamination control strategy (CCS), which Annex 1 requires of every operation. Nevertheless, typical garment systems per grade have emerged.
- GMP A and B: sterile hooded coverall or mandarin-collar coverall with separate sterile hood, sterile overboots, sterile gloves, mask, usually goggles; everything individually packed sterile, changed at every entry.
- GMP C: hood or hair and beard cover, one- or two-piece suit with high collar, suitable shoes or overshoes; non-sterile, low-shedding.
- GMP D: hair and beard cover, general protective clothing, suitable shoes or overshoes.
- ISO 4 to 6 outside GMP: hooded coverall or hood, overboots or cleanroom shoes, gloves, often a mask; material with low particle shedding (Helmke Category I).
ESD-protected cleanrooms in electronics manufacturing add requirements for dissipation: overboots with conductive ribbon, antistatic gloves and materials with defined surface resistivity. More in the guide Standards and PPE Regulation.
How to proceed
- Define class and state: which ISO or GMP class does the room have, at rest and in operation?
- Name the risks: product protection, personal protection or both? Is there splash risk, cytotoxic drugs, biological agents or ESD requirements?
- Choose the delivery condition: sterile for A/B, non-sterile for C/D and most ISO rooms.
- Assemble the system: coverall or frock, hood, overboots, gloves, mask, goggles; parts must match each other.
- Request evidence: data sheet, particle shedding, sterilisation validation, declaration of conformity; for new products the target specification and the test schedule.
Define the garments per class in writing, including gowning order and change interval. A photo per class at the airlock helps new staff and visitors.
Conclusion
ISO classes measure particles in the air; GMP grades add operating state and microbiology. Both systems are related but do not replace each other. For garments: the more critical the class, the more closed, low-shedding and, for A/B, sterile the system must be. Your contamination control strategy documents the decision; the articles' data sheets provide the basis.
Read on: Cleanroom garments as a system: components and gowning order
More in the knowledge section
Go deeper into individual topics: cleanroom classes, garment system, sterility, particle shedding, gloves, masks and standards.
