What Are Cleanroom Classifications?

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  • Written By: Jillian O Keeffe
  • Edited By: A. Joseph
  • Last Modified Date: 12 August 2019
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Cleanrooms are industrial rooms that are cleaner than regular rooms, containing less dust, fewer microorganisms and fewer particles in general than a regular room. Pharmaceutical companies, medical device companies and other types of companies use cleanrooms to manufacture sterile products. Cleanroom classifications vary by regulatory standard, but some of the standards overlap. Each class of a particular standard is allowed to contain a maximum number of particles of a certain size for a specified volume of air. Usually, the specified volume of air is a cubic meter or a cubic foot.

The International Standards Organization (ISO) has cleanroom classifications from ISO 1 to ISO 9, with ISO 1 being the cleanest of all and ISO 9 being the least clean. ISO 1 rooms are allowed to contain no more than 10 particles of 0.1 micrometers per cubic meter of air and no more than two particles of 0.2 micrometers per cubic meter of air.

In some countries, there are several standards applied to cleanrooms, depending on which regulatory standards a factory has to satisfy. For example, the United States uses Federal Standard 209 and ISO Standard, and European factories use ISO standard and European Union pharmaceutical cleanroom classifications, although Great Britain might also use British Standard.


The reason why cleanrooms are classified is that many items, such as drug products to be injected into a vein, need to be sterile. Contamination with microorganisms or particulates can be dangerous for the consumer. Non-sterile products, such as ointments, should be kept as free from contamination as possible, but it is not necessary to package them in a completely sterile manner.

Cleanrooms generally are tested for particles under certain conditions. The standard specifies whether the area is to be at rest, which means that the room is operating as normal but there has been no personnel movement for a specified time, because people can create eddies that kick up settled particles from the floor into the air. An analyst will use a particle meter to draw through the specified volume of air, and the meter will count the particles.

Cleanroom classifications also help divide areas of manufacturing. For example, the European pharmaceutical cleanroom classifications divide areas into Grade D, Grade C, Grade B and Grade A, with Grade A being the cleanest. Grade D is a staging area, where materials are prepared for entry into Grade C. Grade C is where the solution is prepared, and Grade A is where the sterile product is filled. Grade B is the area around Grade A that the filling workers walk around in to transfer the product from Grade C to Grade A.

The U.S. standards range from M1 to M7, with M1 the cleanest class. The M1 limits for 0.1-micrometer particles is 350 per cubic meter and 75.7 0.2-micrometer particles per cubic meter. The British classification system uses the letters C to M, with C the cleanest room. It does not test for particles smaller than 0.1 micrometer and allows up to 100 0.3-micrometer particles.


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