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Updated: May 12, 2021

Peer Review Article | Open Access | Published 10th January 2020

Pharmaceutical Cleanroom Classification using ISO 14644-1 and the EU GGMP Annex 1 Part 1: Testing rationale

T Eaton AstraZeneca, Macclesfield, UK | EJPPS | 244 (2020) | Cite this article | Click to download pdf


Cleanroom classification is an essential part of the qualification activities in pharmaceutical cleanrooms that confirm the effectiveness of the cleanroom’s airborne contamination control system. A review of the classification requirements and principles associated with ISO 14644-1:2015 and the 2008 version of Annex 1 of the EU GGMP is contained in this first article, and a suitable classification test method derived for aseptic manufacturing. A second article will consider the application of the method by means of practical examples.


Cleanroom classification, ISO 14644-1, EU GGMP Annex 1

1. Introduction

All cleanrooms are classified according to ISO 14644-1 (1) to demonstrate that a specified concentration of airborne particles is not exceeded. Annex 1 of the European Union Guide to Good Manufacturing Practice (EU GGMP) (2) specifies the environmental conditions that must be provided for the manufacture of sterile medicinal products and requires that the classification of different grades of cleanrooms and clean zones be based on ISO 14644-1.

The classification of pharmaceutical cleanrooms or clean zones is an essential part of the qualification process to ensure that appropriate levels of airborne contamination are provided for the type of activities undertaken. In addition, the classification can provide useful reference data if any future modifications to the cleanroom or its ventilation system are completed, or an investigation is undertaken to determine the reasons for any system deterioration. However, the correct interpretation and application of the information given in ISO 14644-1 and Annex 1 of the EU GGMP, as well as consideration of more current expectations from the regulatory authorities, is required and included in this article. Although the classification method is applied to cleanrooms used for aseptic manufacture, the approach can be used for most pharmaceutical and healthcare cleanroom applications with some minor modifications.

2. Origins of the cleanroom classification standard

The standard that most influenced the early establishment of the correct design and operation of cleanrooms was United States’ Federal Standard 209 (FS 209), entitled ‘Cleanroom and Work Station Requirements, Controlled Environments’ which was first published in 1963 and considered both unidirectional airflow (UDAF) and non-UDAF cleanrooms.

The class limits given in FS 209 were established by airborne particle number concentration measurements carried out in a large number of cleanrooms used for many activities, including electronic component and pharmaceutical manufacturing, mainly in the United States. Several revisions of FS 209 were undertaken up to revision D, which was published in 1988. All these revisions included cleanroom class limits based on the number of particles ≥0.5 μm per ft³ of cleanroom air. The final version E, had class limits that were additionally reported as concentrations per m³. This standard was withdrawn in 1992 after the International Organization for Standardization (ISO) published ISO 14644-1: 1999 to produce worldwide harmonization. This ISO standard is the basis of the current ISO 14644-1: 2015 standard and also for the airborne particle concentrations included the EU GGMP.

The relationships between the particle number concentration and the threshold particle size(s) that are used to set the class limits in ISO 14644-1 were established in the early 1960s. At that time, conditions in cleanrooms were different from modern cleanrooms and, for example, cotton garments were often used and the methods of counting and measuring particles were in their infancy. Consequently, airborne particle count distributions and class limits that were used, and still used, in ISO 14644-1 and the EU GGMP for cleanrooms and clean zones, are likely to be different from those found in modern healthcare cleanrooms. This difference may cause difficulties when measuring the airborne particle concentrations and applying class limits. The problem is discussed further in the second article (3).

3. Classification of an EU GGMP (2008) cleanroom in accordance with ISO 14644-1: 2015

Annex 1 of the EU GGMP (2008) states that cleanrooms and clean air devices should be classified in accordance with ISO 14644-1. However, since the publication of that guide some additional requirements are expected by the regulatory authorities and may be included in the revised edition of EU GGMP when published. 

It should be noted that the ISO 14644-1: 2015 standard refers to cleanrooms and clean zones and Annex 1 of the EU GGMP (2008) refers to cleanrooms and clean air devices. These clean air devices typically include isolators, restricted access barrier systems (RABS), open access safety cabinets etc. and when utilised for critical activities, are required to meet the contamination control requirements of an EU GGMP Grade A environment. For simplicity, this paper often refers to ‘cleanrooms’, when the term covers both cleanrooms and clean air devices.

The EU GGMP requires the classification of a cleanroom to be carried out in the ‘at rest’ and ‘in operation’ states. The ‘in operation’ classification state relates to the actual manufacturing process and provides the most useful information, and it is therefore the focus of this paper. However, the ‘at rest’ classification state, which requires a similar approach, is also discussed.

Table 1 summarises the classification requirements and principles contained in ISO 14644-1: 2015 and Annex 1 of the EU GGMP (2008) that is relevant to this article, along with information on the current expectations of the regulators that are additional to EU GGMP (2008). These provide a classification testing rationale for pharmaceutical cleanrooms used for aseptic manufacture.

4. Discussion and conclusions

Classification is an essential part of the cleanroom qualification activities in pharmaceutical cleanrooms to provide information regarding appropriate control of airborne contamination. A review of the classification requirements and principles associated with Annex 1 of the EU GGMP (2008) and ISO 14644-1 (2015) has been discussed in this paper as well as some more recent regulatory authority expectations. With an understanding and interpretation of these requirements, and the cleanroom operational activities and type of airflow utilised to achieve control of airborne contamination, the correct approach for pharmaceutical cleanrooms classification has been derived. If this approach is followed, it will provide meaningful reference information regarding the effectiveness of the cleanroom’s airborne contamination control system under worst-case operational conditions. This information will also provide essential reference data should the cleanroom or ventilation system be modified, or the manufacturing activities changed, and to confirm the effectiveness of the airborne contamination control system relative to the original state.


01. ISO 14644-1: 2015 Cleanrooms and associated controlled environments - Part 1: Classification of air cleanliness. Geneva, Switzerland, International Organization for Standardization, 2015.


02. The rules governing medicinal products in the European Union –Volume 4 EU guidelines to good manufacturing practice - medicinal products for human and veterinary use - Annex 1 -Manufacture of sterile medicinal products. European Commission, Brussels, 2008.


03. Eaton T . Pharmaceutical Cleanroom Classification using ISO 14644 and the EU GGMP Annex 1; Part 2: Practical application. European Journal of Parenteral and Pharmaceutical Sciences 2019; 24(4).


04. Eaton T. Annex 1 of the EC Guide to Good Manufacturing Practice (EC GGMP) and continuous particle monitoring - help or hindrance for cleanroom manufacturing? European Journal of Parenteral & Pharmaceutical Sciences 2007; 12(2): 29-37.


05. Whyte W. and Hejab M. Dispersion of particles and microorganisms from people. European Journal of Parenteral and Pharmaceutical Sciences 2007; 12 (2): 39- 46.


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07. Particle Measuring Systems (PMS) Inc., Application Note 201 2/2018. Particle Transportation 2018. Available at


08. Standard practice for continuous sizing and counting of airborne particles in dust-controlled areas and clean rooms using instruments capable of detecting single sub-micrometre and larger particles. ASTM F50-12 (2015). ASTM International, 2015.


09. Food and Drug Administration. Guidance for Industry: Sterile Drug Products Produced by Aseptic Processing – Current Good Manufacturing Practice. Silver Spring, MD, USA: FDA; 2004.


10. ISO 21501-4: 2018 Determination of particle size distribution - Single particle light interaction methods - Part 4: Light scattering airborne particle counter for clean spaces. Geneva, Switzerland, International Organization for Standardization, 2018.


11. Whyte W, Whyte WM, Ward S and Agricola K. Ventilation effectiveness in cleanrooms and its relationship to decay rate, recovery rate, and air change rate. European Journal of Parenteral and Pharmaceutical Sciences 2018; 23 (4): 126-134. Available at


12. BS EN ISO 14644-2: 2015 Cleanrooms and associated controlled environments - Part 2: Monitoring to provide evidence of cleanroom performance related to air cleanliness by particle concentration (ISO 14644-2:2015). London, England, British Standards Institution, 2015.


13. Whyte W. Advances in cleanroom technology. 2018. Euromed communications. ISBN 978-0-9956666-6-5.


14. Whyte W, Hodgson R and Bailey PV. The sources of contamination in bottles of infusion fluid. The Pharmaceutical Journal, August 25, 1979, pp 173-174.


15. Whyte W. A multicentred investigation of clean air requirements for terminally sterilised pharmaceuticals. Journal of Parenteral Science and Technology 1983; 37(4): 138-144.

Appendix A: ISO 14644-1 and EU GGMP Annex 1 room occupancy definitions


a. Annex 1 of the EU GGMP refers to ‘in operation’ and the ISO 14644-1 standard refers to ‘operational’ but these two terms are considered to be equivalent.

Appendix B: ISO 14644-1:2015 and EU GGMP Annex 1 (2008) airborne cleanliness concentrations

Shown in Table B1 are the airborne cleanliness concentrations for particles ≥0.5 μm and ≥5 μm given in ISO 14644-1 and the EU GGMP Annex 1 (2008). It should be noted that ISO standard 14644-1 allows airborne classification in three occupancy states and the associated occupancy state must be stated. Annex 1 of the EU GGMP only considers two occupational states. Shown in the table are the ISO 14644-1 concentrations considered to correspond with the EU GGMP Annex 1 concentrations for the ‘at rest’ and ‘in operation’ occupancy states.


a. Sample collection limitations for both sizes of particles in low concentrations and sizes greater than 1 μm make classification at this particle size inappropriate, due to potential particle losses in the system.

b. The ‘in operation’ concentrations for EU GGMP Grade D areas are not defined, and the user is expected to set their own limits. As the ‘at rest’ limits are typically easily attainable for ‘in operation’ conditions, the ‘at rest’ limits are often also applied to the ‘in operation’ state.

Appendix C: Table in ISO 14644-1:2015 used to obtain minimum number of samples in a cleanroom

Appendix D: Calculation of number of air sampling locations required for cleanroom classification 

To classify a cleanroom according to ISO 14644-1:2015, airborne particle sampling must be carried out across the cleanroom. The number of sampling locations is related to the surface area of the floor and given in Table A1 of ISO 14644-1 (reproduced in Appendix C of this article). ISO 14644-1 suggests that the floor area should be divided into equal sized areas where sampling is carried out. This is relatively simple to achieve in a cleanroom that is square or rectangle but difficult where the floor area is asymmetrical. However, ISO allows additional sections to be added to facilitate subdivision into equal sections. The ISO standard does not give information about how this sub-division can be carried out but the following method can be used.

1. Divide the asymmetric floor or base area of the cleanroom or clean zone into suitable sizes of rectangular sub-area. Start with the largest rectangle that can be accommodated and work towards the smallest.

2. Add together the floor surface areas (m²) of the sub-areas to obtain the total floor area of the cleanroom.

3. Calculate the number of sampling sections in each sub-area using the following equation;

Number sections in sub-area = (floor area of sub-area) x minimum no. sampling locations

(total floor area)

Where, the ‘minimum no. of sampling locations’ is equal to the number of equal-sized sampling sections required for total floor area that is obtained from Table A1 of ISO 14644-1 (reproduced in Appendix C of this article).

These results should be rounded up to whole numbers (any number less than 1 should be assumed to be 1). Ensure that the total of these results is greater that the number required by ISO 14644-1.

4. Starting with the largest sub-area, divide its cleanroom floor area by the number of sampling sections required in its area. This will give the surface area of the sampling section and, taking account of the sampling requirements, the length and width of the sampling sections should be decided.

5. An example of the above method is given in the second part of this article³.

Using the formal risk assessment methods discussed in Appendix E of this article, the sampling locations within each section can be identified, and particle sampling carried out.

Appendix E: Use of risk assessment to select sampling locations 

Annex 1 of the EU GGMP (2008) requires the classification of a cleanroom or clean zone to be carried out according to the method given in ISO 14644-1. ISO 14644-1: 2015 recommends that the floor area of a cleanroom or clean zone is divided into sections, and airborne sampling carried out at locations representative of the conditions in the sections. However, the current expectations of the regulatory authorities is for sampling to be carried out where the risks from airborne contamination are highest. In clean air devices (EU GGMP Grade A, hereafter referred to as workstations), the chosen locations should be in proximity to critical surfaces, such as where product, components or product contacting surfaces, are exposed to airborne contamination. In cleanrooms that contain the clean air device, the sampling positions should be where the highest particle concentrations associated with personnel activity are located. In cleanrooms outside the aseptic processing room, the sampling should be carried out in representative locations without the need for a risk assessment.

Selection of sampling locations by risk assessment in critical workstation

Information about various risk assessment methods used in cleanrooms is available elsewhere (13). It is explained that the level of risk from contamination can be calculated by the following equation:

Risk = Severity x Occurrence Equation E.1

Severity; The importance, or seriousness, of an event. In the situation where the level of risk of airborne contamination to vulnerable surfaces, such as product, is required, the risk can be calculated by use of the following risk factors.

1. The likely particle airborne concentrations at a critical surface; However, this will not be known, but descriptors can be used as surrogates for the airborne concentration. These descriptors are (a) personal activity and, therefore, the dispersion rate of particles, and (b) the effectiveness of the ventilation system in reducing the airborne particle concentration.

2. The surface area of the critical surface that is exposed to airborne deposition.

It should be noted that only the airborne contamination dispersed from personnel is considered in this risk assessment, and not that from machinery or equipment. This will simplify the risk assessment and is consistent with the demonstrated fact (14) (15) that the most important contaminant in pharmaceutical cleanrooms is microbial, and not small inert particles. However, large sources of particles emitted from machines may influence the actual particle concentrations measured during classification and this should be considered when the sampling results are collected.

Occurrence; The frequency that the event occurs. In the case of airborne contamination, it is the time that the critical surface, such as product or product contacting surface, is exposed to airborne contamination.

An example of the descriptors of the risk factors, and the risk scores that can be assigned to the descriptors when assessing the risk of contamination, are given in Table E1.

The level of risk at each location can then be obtained by the equation E.1; 

Risk = Severity x Occurrence

= (Personnel activity score x Ventilation type score x Surface exposed) x Time exposed

An example of the use of this method is given in Appendix B in the second article (3).

Selection of sampling locations in the cleanroom containing a workstation

For cleanrooms in which the clean air device is located and, therefore, critical surfaces are not directly exposed to airborne contamination, the sampling locations should be where the highest airborne concentrations of particles are found. As discussed previously, the emission of particles from machinery and equipment is likely to affect the particle concentration but only personnel need to be considered. An example of the use of this method is given in Appendix A in the second article.

Cleanrooms adjacent to the aseptic processing room

For lower Grades of cleanrooms that are adjacent to the aseptic processing room, samples should be taken at locations that are representative of conditions in each of the sections obtained by the procedure discussed in Appendix D. There is no need for a risk assessment.


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