What is a pharmaceutical clean room? Well, it’s a straightforward question with a straightforward answer. A pharma clean room is simply an especially clean space, with no contamination or infiltration, for use in the development of medicine or medical processes.

Or is it? As with many things, especially in the pharma field, the answer is not quite so clean cut.

Yes, a clean room is space that has been cleaned of and safeguarded against contaminants. But are all clean rooms equal? No, they are not.

Let’s take a look at some of the different classifications of clean rooms to help you get to grips with what the concept can really mean. This will help you ensure the safety and hygiene of your pharma manufacturing and testing equipment.

The ISO Scale

In the USA and Canada, clean rooms are assessed according to the ISO scale.

In 1999, the ISO-14644-1 scale was introduced, and is now the de facto measurement of how “clean” a clean room really is.

The classes on this scale are as follows:

  • ISO 1 (The cleanest end of the scale)
  • ISO 2
  • ISO 3
  • ISO 4
  • ISO 5
  • ISO 6
  • ISO 7
  • ISO 8
  • ISO 9 (The dirtiest end of the scale)

It is worth mentioning that, while ISO 9 is the “dirtiest” of all the clean room classifications, it is still considerably cleaner than a standard space! It is still worth knowing how your clean room ranks so you can achieve the best results with your equipment, though.

What the ISO Scale Classifications Actually Mean

The different classifications are defined according to the amount of particles found in the air in each space. However, each classification also takes into account the size of each particle.

In order for a clean room to be considered ISO 1, it must have:

  • 10 or fewer particles of 0.1 µm (microns) or less in size
  • 2 or fewer particles between 0.1. µm and 0.2 µm

Take a look at the table below to learn more about these classifications.

ISO Class# of particles of 0.1 µm
(or smaller)
(or smaller)
0.3 µm
(or smaller)
(or smaller)
1 µm
(or smaller)
5 µm
(or smaller)
ISO 1102
ISO 210024104
ISO 31,000237104
ISO 410,0002,370102358
ISO 5100,00023,70010,2003,5208329
ISO 61,000,000237,000102,00035,2008,320293
ISO 7352,00083,2002,930
ISO 83,520,000832,00029,300
ISO 935,200,0008,320,000293,000

*Please note that any values not filled in above are simply not required for classification at that level. For example, particles of 0.3 µm and above cannot be present in a clean room of ISO 1 classification. Any trace of a particle of that size will automatically move the clean room up to the next ISO class.

**Similarly, filtration for particles of 0.3 µm or less is considered too precise for ISO classes 7, 8 and 9, and particles of this size will simply not be taken into account.

Clean Rooms and Air Recirculation

Clean room classifications relate to the amount of particles found in the air within the space. As long as the particle levels listed above are achieved, there are no hard and fast rules regarding how this is done.

However, most spaces classed as clean rooms will meet certain standards regarding air recirculation. This is because air that is not recirculated or is left unchanged for a long period of time is unfiltered, and therefore may carry contaminants.

Generally, the air in an ISO 5 class clean room will be changed and filtered between 240 and 360 times per hour. For an ISO 6 class space, this drops to between 90 and 180 times per hour, 30 to 60 times per hour for ISO 7, and 10 to 15 times per hour for the ISO 8 category.

By comparison, a conventional building with an HVAC system undergoes two to four complete changes of its air each hour.