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Particle Release of ICR Plates for Environmental Monitoring During Use in Cleanrooms

Settle plates and contact plates are commonly used for the environmental monitoring of cleanrooms. The ISO 14698 guideline states: “When culture media are used in cleanrooms, the external surface of their containers shall be maintained in a state of cleanliness appropriate to their use.” This requirement is usually discussed with the microbiological contamination risk of these products. Hence, all cleanrooms are qualified and monitored for particles that define the cleanliness of the air.

ICR plates are intended to be used in cleanrooms grade A with particle limits as described for ISO 5 cleanrooms (ISO 14644). The result of this article shows that the handling of plates (unpacking and removing the desiccation bag) will not exceed the limits for cleanroom particles Grade A acc. Annex 1.

The ICR culture media in settle or contact plates are designed for use in cleanrooms, RABS, and isolators. They are triple bagged in a transparent and VHP impermeable bag. The inner bag is sealed with 10 media plates and a desiccant sachet. After the removal of the 2 outer bags in material locks, the innermost single bag is ready to be used in a cleanroom ISO 5 or isolator.

In this article, the particle emission of the packaging material of ICR plates in cleanrooms is studied. The results verify that the removal of the inner packaging material including the desiccant will not emit 0.5 µm particles that exceed the limits for an ISO 5 cleanroom environment.

Test procedure & acceptance criteria

The particle emission test was performed following ISO 14644-14 to assess the suitability for use of equipment regarding airborne particle concentration. 30 bags each of either 10 contact or settle plates were used. 5 test runs were performed per batch of culture media. The selection of the media batches was performed based on the maximum variety of different desiccant batches from 2 different suppliers.

  • Batch 1: LI-settle plate (includes desiccant batch 1 of supplier A) – this is a non-irradiated single bagged version of plates, but with same bag material and desiccant as ICR plates and can be classified as worst case
  • Batch 2: ICR-settle plate (includes desiccant batch 1 of supplier B)
  • Batch 3: ICR-settle plate (includes desiccant batch 2 of supplier B)
  • Batch 4: ICR-contact plate (includes desiccant batch 1 of supplier A)
  • Batch 5: ICR-contact plate (includes desiccant batch 1 of supplier B)
  • Batch 6: ICR-contact plate (includes desiccant batch 2 of supplier B)

A background read in the laminar flow hood with the particle counter was performed before starting a set of particle emission tests (5 tests per plate batch) After unwrapping the outer two bags outside of the hood, the innermost bag was placed 10 cm away from the isokinetic probe of a particle counter and the particle measurement was started. 15 seconds later, the bag was torn open and the plates were removed. The desiccant sachet was then placed on the top of the plate empty bag.

The workflow is illustrated in a series of images as seen in Figure 1.

particle emission test

Step 1.Particle emission test set up

Opening of the plate staple

Step 2.Opening the plate staple

Removal of bag

Step 3.Removal of the bag

Moving desiccant to the top

Step 4.Moving the desiccant to the top

Figure 1. Performance of particle emission test at a distance of 10 cm.

The average particle emission upon opening of the inner bag of 10 plates including the movement of the desiccant should conform to ISO class 5 conditions: ≤ 3520 particles per m3 at a size of 0.5 µM.

Suitability of ICR Plates with Desiccant in ISO Class 5 Cleanroom

The background read was zero in all cases. All tests conformed to the specified particle limit of a maximum of 3520 particles at a size of 0.5 µM per m3. All single results are shown in Figure 2. The highest single count was 250 x 0.5 µM particles. The average of all 30 test runs was 19 x 0.5 µM particles, which were emitted during the process of unpacking culture media and moving the desiccant sachet.

desiccant sachet

Figure 2.Graph illustrating the number of 0.5 µM particles emitted during unpacking plates and removing desiccant sachet.

These results confirm the suitability of the ICR plates with desiccant in cleanroom environments up to ISO 5 classification. Nevertheless, it is recommended to perform the unpacking of the culture media plates as far away from critical manufacturing areas (i.e. open product) as possible.

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ISO 14644-1: Cleanrooms and associated controlled environments –(2015). [Internet]. Part1: Classification of air cleanliness by particle concentration(2016): Available from:
ISO 14644-14 Cleanrooms and associated controlled environments: 2016. [Internet]. Part 14: Assessment of suitability for use of equipment by airborne particle concentration: Available from:
ISO 14698-1 (2003): Cleanrooms and associated controlled environments-Biocontamination control. [Internet]. Part1: General principles and methods: Available from: