ISO 14644 vs. GMP Annex 1: The Definitive Guide to Compliance

Introduction: GMP Grades or ISO Classes? Let's Clear the Air

In the world of pharmaceutical manufacturing, especially in sterile environments, air management is everything. The invisible enemy is contamination, whether particulate (non-viable) or microbiological (viable). To control this enemy, the industry relies on two regulatory pillars: the ISO 14644 series and, for Europe, GMP Annex 1 (Manufacture of Sterile Medicinal Products).

For many professionals, the relationship between these two documents is confusing. We hear about "Grade A" and "Grade B," but also "ISO 5" and "ISO 7." Are these the same thing? If I comply with ISO 14644, do I automatically comply with Annex 1? And what has changed with the 2022 revision of Annex 1 regarding the infamous 5-micron particles?

Understanding this relationship is not an academic exercise. It is essential to properly design, qualify, and monitor cleanrooms, avoiding critical findings during EMA, AIFA, or FDA inspections.

Poor design or monitoring that doesn't meet regulatory expectations can lead to batch rejects, costly HVAC system retrofits , and, in the worst case, patient safety risks.

The Fundamental Relationship: What (GMP) vs. How (ISO)

The simplest and most effective distinction to understand the relationship is this:

• GMP Annex 1 says WHAT you need to achieve.

It defines the regulatory requirements for sterile production. It establishes the maximum levels of contamination (particulate and microbiological) permitted for various activities, dividing them into Grades: A, B, C, and D. Grade A is the cleanest (critical zone), Grade D is the least clean (support area).

• ISO 14644 says HOW you should measure it.

It is an international technical standard that defines the methodology for classifying and testing a cleanroom based solely on particulate contamination (non-viable). It defines the ISO Classes (1 to 9).

Annex 1 itself (2022 revision) makes the link, explicitly stating that cleanrooms must be classified according to ISO 14644-1 to determine the number of sampling points and methodology ¹ .

In practice: you use the ISO 14644-1 method to demonstrate that you have achieved the GMP Annex 1 requirement .

The Conversion Table: GMP Grades vs. ISO Classes

Annex 1 provides a table (updated to 2022) that links GMP Grades to the particle limits of the ISO Classes.

GMP Grade	State	Particles ≥0.5 μm/m3	Particles ≥5 μm/m3	ISO class approx.
Grade A	At rest / Oper.	3,520	20	ISO 4.8 (more severe than ISO 5)
Grade B	At rest	3,520	29	ISO 5
Grade B	In operation	352,000	2,900	ISO 7
Grade C	At rest	352,000	2,900	ISO 7
Grade C	In operation	3,520,000	29,000	ISO 8
Grade D	At rest	3,520,000	29,000	ISO 8
Grade D	In operation	Undefined*	Undefined*	(Monitoring only)

Note: The 2022 revision of Annex 1 introduced the limit of 20 particles/m³ (for $\ge5~\mu m$) in Grade A, making it technically an "ISO 4.8", slightly more stringent than the classic ISO 5 ² .

The 5 Micron Challenge: Classification vs. Monitoring

The most discussed novelty introduced by the 2022 revision of Annex 1 concerns the management of $\ge5~\mu m$ particles in Grade A and B. This point derives from a scientific alignment with ISO 14644-1:2015 itself.

The Scientific Problem (ISO 14644-1):

The ISO standard has recognized that, in ultra-clean environments (such as ISO 5), the particle number $\ge5~\mu m$ is so low (e.g., <29/m³) that statistical sampling becomes unreliable. A single "false positive" (due to electronic instrument noise, or a random event) can cause classification to fail3.

The Annex 1 Solution (2022):

Annex 1 has acknowledged this scientific criticality and introduced a crucial distinction44:

1. Classification (Initial Qualification): For formal Grade A/B classification (the initial or periodic "at rest" qualification activity), the particle count  is no longer the determining factor and may be optional, provided compliance on $\ge0.5~\mu m$ ⁵⁵ is demonstrated. The objective of the classification is to demonstrate that the HVAC system and HEPA filters are operating as designed (the "at rest" state).
2. Monitoring (In Operation): For monitoring during production (state "in operation"), the $\ge5~\mu m$ particles remain mandatory and fundamental  .

Why this distinction?

During production, the source of particulate matter (often carrying microbes) is not the HEPA filter, but the operator or the process. Detecting even a single particulate matter event during "in operation" monitoring is no longer "statistical noise," but a critical alarm signal (e.g., an operator moved too abruptly, there was a gowning problem) that requires investigation.

Not just ISO 14644-1: The Importance of the Complete Series

A common mistake is to limit yourself to ISO 14644-1 (Classification) and ISO 14644-2 (Monitoring). But the ISO 14644 series offers much more, providing practical tools for GMP compliance.

• ISO 14644-3 (Test Methods):

This is the standard for HVAC system qualification (OQ/PQ). It defines how to perform essential tests required (implicitly or explicitly) by Annex 1:

• • HEPA Filter Integrity Test (Essential)
  • Testing pressure differentials between rooms
  • Flow Visualization ( Smoke Test )
  • Recovery Time Test
  • Air velocity measurement (in unidirectional flows Grade A)
• ISO 14644-4 (Design):

Guides the design of the cleanroom: layout, construction materials (smooth, cleanable, non-porous), personnel and material flows, pressure cascades8.

• ISO 14644-5 (Operations):

Defines the "rules of behavior" in the cleanroom: dressing procedures, cleaning techniques, staff behavior (slow movements), materials management 9.

• ISO 14644-7 (Separative Devices):

Extremely important for Annex 1, which encourages the use of isolators and RABS. This standard defines the design and testing requirements for these barriers.

Career Impact: From Performer to CCS Expert

The 2022 revision of Annex 1 introduced the comprehensive concept of Contamination Control Strategy (CCS) . The CCS is a strategic document that describes all the measures implemented to control contamination.

A professional (QA, Validation, Manufacturing) who understands how the ISO 14644 series (design, testing, classification, monitoring, operations) integrates to build the CCS becomes a key figure in the company. They don't just "count particles," they understand why they count them, where to count them, and what to do with that data.

FAQ: Frequently Asked Questions about ISO 14644 and Annex 1

Q1: My cleanroom is "ISO 7". Does it correspond to Grade B or C?

It depends on the state. An ISO 7 area (boundaries $\ge0.5~\mu m$) can correspond to a Grade B "in operation" OR a Grade C "at rest"11. It is essential to always specify the state (at rest / in operation) when making a comparison.

Q2: Do I need to reclassify my cleanroom every year?

Yes. Annex 1 (and ISO 14644-2) require periodic re-classification (usually annually for Grade A/B, or every 2 years for C/D, but Annex 1 pushes for annually) to confirm that the HVAC system is still performing (at rest status).12 This is different from monitoring, which is continuous/frequent.

Q3: If I use an Isolator (Grade A), what Grade should the room (background) be?

Annex 1 (and ISO 14644-7) specifies that if the isolator operates in a "closed" mode (never opened during the process), the background can be a Grade D. If it is a RABS (which can open), the background must be at least a Grade B13.

Q4: Does ISO 14644 also cover microbiological monitoring?

No. The ISO 14644 series focuses on particulate matter (non-viable)14. The control of biocontamination (microbes) is covered by Annex 1 (which gives limits in CFU/m³ and per plate) and, technically, by the ISO 14698 series (Biocontamination control).

Conclusion

ISO 14644 and GMP Annex 1 are not in conflict; they complement each other. Annex 1 establishes the quality objectives for sterile manufacturing (the Grades), while the ISO 14644 series provides the technical toolkit (the Classes and test methods) to achieve and demonstrate those objectives.

Understanding the critical distinction between classification and monitoring, especially for $\ge5~\mu m$ particles, is today the minimum requirement for managing a sterile area compliantly and efficiently.

For a complete operational guide on how to implement all ISO 14644 tests (from smoke testing to HVAC qualification) and build a monitoring plan compliant with the new revision of Annex 1, discover the complete guide " Operational Guide to the ISO 14644 Series " on GuideGxP.com.