What is class 5 ISO?

Class 5 ISO refers to a cleanroom classification system that specifies the amount of airborne particles permitted in a controlled environment. Cleanrooms are used extensively in industries like semiconductor manufacturing, pharmaceutical production, and medical device development that require extremely high levels of cleanliness and control over environmental contaminants.

Overview of Cleanroom Classifications

Cleanrooms are classified based on the concentration of airborne particles per volume of air. There are two major standards used to classify cleanrooms: ISO 14644-1 and Federal Standard 209E. Both standards measure particles in sizes ranging from 0.1 to 5.0 microns, but they use slightly different concentration limits at each classification level.

Federal Standard 209E classes cleanrooms from 1 to 100, with higher numbers denoting cleaner environments. ISO 14644-1 uses a scale from ISO Class 1 to ISO Class 9, with ISO Class 1 representing the highest level of cleanliness. The ISO system has largely replaced the older Federal Standard.

While the two standards differ somewhat in their concentration limits, ISO Class 5 is approximately equivalent to the old Federal Standard Class 100. However, ISO 14644-1 is considered the more precise and thorough system today.

ISO 14644-1 Cleanroom Classifications

Here are the concentration limits for the major ISO 14644-1 cleanroom classifications:

ISO Class Maximum particles/m3 ≥0.1 μm Maximum particles/m3 ≥0.2 μm Maximum particles/m3 ≥0.3 μm Maximum particles/m3 ≥0.5 μm Maximum particles/m3 ≥1 μm Maximum particles/m3 ≥5 μm
ISO Class 1 10 2 1 1 0 0
ISO Class 2 100 24 10 4 1 0
ISO Class 3 1,000 237 102 35 8 0
ISO Class 4 10,000 2,370 1,020 352 83 0
ISO Class 5 100,000 23,700 10,200 3,520 832 29
ISO Class 6 1,000,000 237,000 102,000 35,200 8,320 293
ISO Class 7 352,000 83,200 2,930
ISO Class 8 3,520,000 832,000 29,300
ISO Class 9 35,200,000 8,320,000 293,000

As shown in the table, the concentration limits get progressively higher (less clean) with each ISO class. The measurement thresholds also capture smaller and smaller particle sizes at the higher ISO classes.

ISO Class 5 Parameters

Looking specifically at ISO Class 5, we can see it allows for:

  • 100,000 particles per cubic meter 0.1 μm or larger
  • 23,700 particles per cubic meter 0.2 μm or larger
  • 10,200 particles per cubic meter 0.3 μm or larger
  • 3,520 particles per cubic meter 0.5 μm or larger
  • 832 particles per cubic meter 1.0 μm or larger
  • 29 particles per cubic meter 5.0 μm or larger

Particles in the range of 0.1 to 5.0 microns are typical airborne contaminants of concern in cleanrooms. This includes skin cells, cosmetics, dust, clothing fibers, and microorganisms. While an ISO 5 cleanroom allows more particles than lower classifications, it still ensures a remarkably high level of cleanliness compared to ambient conditions.

Applications of ISO Class 5 Cleanrooms

ISO Class 5 cleanrooms provide sufficient control over particles for a wide range of industries and applications:

Pharmaceutical Manufacturing

Many aseptic pharmaceutical processes take place in ISO 5 cleanrooms. This includes steps like sterile powder handling, product transfer, sterile filtration, filling operations, and packaging. Maintaining an ISO Class 5 environment helps minimize risks of particulate contamination while making injectable drugs, ophthalmics, and other sterile products.

Medical Devices

Strict cleanliness is essential when manufacturing implantable devices like pacemakers, prosthetic joints, cardiac stents and other items that will be surgically inserted into the human body. ISO 5 cleanrooms are commonly used for production of Class II and Class III medical devices to reduce potential introductions of microbes or foreign debris.

Disk Drive Manufacturing

Hard disk manufacturing facilities utilize ultraclean environments, including ISO 5 cleanrooms, to prevent even microscopic dust particles from being sealed inside disk drive components. Airborne particles can damage drive surfaces and corrupt read/write operations.


Production of silicon wafers, semiconductors and other microelectronics frequently employs ISO Class 5 cleanrooms. Airborne particles can ruin the tiny features on microchips and other devices. Maintaining highly controlled conditions minimizes defects.


Sensitive aerospace systems like gyroscopes, sensors and optics are assembled in ISO 5 cleanrooms. This prevents foreign object debris issues that could arise if particulates entered these precision systems, damaging functionality.


Hospital pharmacies often maintain ISO Class 5 cleanrooms for preparing sterile compounds like chemotherapy drugs, total parenteral nutrition solutions, and ophthalmic formulations. This protects vulnerable patients from harmful particulate contaminants.

Design and Construction of ISO Class 5 Cleanrooms

Achieving an ISO Class 5 environment requires careful cleanroom design, construction and operation. Some key considerations include:

Air Filtration

ISO 5 cleanrooms use HEPA or ULPA fan filter units to remove airborne particles. Air is constantly recirculated through these filters to trap particles before they can enter the cleanroom space.

Air Changes Per Hour

Frequent air changes are needed to flush contaminants out of an ISO 5 cleanroom. Typically 60-90 air changes per hour are recommended.

Airflow Patterns

Cleanrooms are designed with specific airflow patterns, often using a turbulent flow to continually sweep particles away from the work zone.

Room Pressurization

ISO 5 cleanrooms are kept at a slightly higher pressure than surrounding areas. This causes air to flow outwards from the cleanroom, preventing unfiltered particles from infiltrating.

Gowning Requirements

Personnel entering an ISO Class 5 cleanroom must pass through gowning rooms where they don appropriate protective garments (like coveralls, hoods, boots, gloves) to minimize contamination from their bodies.

Materials of Construction

Cleanroom structures are built from smooth, non-shedding materials. Metals, vinyl, epoxy paint and other easily sanitized surfaces are common.

Airlocks & Interlocking Doors

Airlocks and interlocking pass-through doors are incorporated into ISO 5 cleanroom design. These mechanisms prevent room pressures from equalizing and outside air from entering when doors are opened.

Maintaining ISO Class 5 Conditions

Once an ISO 5 cleanroom is constructed, continual monitoring and maintenance is required to ensure standards are met on an ongoing basis. Important aspects of cleanroom operation include:

Routine Recertification

Cleanrooms undergo periodic testing and recertification to validate they are staying within ISO 5 specifications. This involves particulate counting and environmental monitoring.

Filter Changes

Filter loss can allow more particles to penetrate the cleanroom, so HEPA/ULPA filters must be replaced per the manufacturer’s recommendations.

Cleaning & Disinfection

Thorough cleaning and disinfection protocols eliminate particles that could get resuspended in the air. Surfaces are regularly wiped down with IPA, bleach or other approved disinfectants.

Gowning Audits

Personnel gowning procedures are audited to ensure proper techniques are followed. Poor gowning can allow many particles to be carried into the cleanroom.

Repairs & Maintenance

Any leaks, cracks or other problems are immediately repaired to avoid cleanroom degradation. Facilities management maintains electrical, ventilation and other systems.

Traffic Control

Cleanroom entry is restricted only to necessary personnel and materials to minimize contamination. ISO 5 cleanrooms also have strict requirements about what can be brought inside.


ISO Class 5 cleanrooms provide a carefully controlled environment with extremely low levels of airborne particles measuring 0.1 μm and larger. While not as stringent as higher ISO classes, ISO 5 specifications offer sufficient cleanliness for a wide range of manufacturing and research settings that require protection from particulate contamination.

Achieving an ISO 5 rating demands meticulous cleanroom design, construction and operation. Continuous monitoring and disciplined contamination control procedures are necessary to maintain these stringent cleanliness levels on an ongoing basis.