What is a Cleanroom?

A cleanroom is a room that is free from dust and other contaminants. Cleanrooms are required in various applications, in varying cleanroom ratings, including food & process manufacturing, electronics and IT, pharmaceutical, medical, and healthcare. Cleanrooms have specific requirements to achieve different rating levels, governed by organizations like the FDA and ISO. Common aspects of cleanrooms are air filtration, air quality, and air condition control.

Kinds of Cleanrooms

Hardwall Cleanrooms

Hardwall cleanrooms utilize hard, rigid wall structures. These types of cleanrooms are completely enclosed and employ air vents to remove air. If higher pressure differentials are required, including negative and positive/negative pressure cleanrooms, then hard wall cleanrooms are required. In order to meet higher classifications of cleanrooms, hardwalls may be required. Additionally, cleanrooms where air conditioning and humidity control is required must be hardwall. Hardwall cleanrooms are typically made from acrylic, static-dissipative PVC, polycarbonate, and polypropylene.

Softwall Cleanrooms

Softwall cleanrooms utilize a simple steel frame structure that supports plastic curtains that leave space at the floor for exhausting air. Softwall cleanrooms can provide low positive pressures and are great for lower cleanroom classifications such as Class 1000, 10,000, and 100,000. These cleanrooms are great because they are semi-permanent and can easily be moved, broken down, or constructed.

How does a Cleanroom Work?

Positive Pressure

Positive Pressure Cleanrooms work by pumping in air through fan-filter units, typically on the ceiling, forcing air through HEPA or ULPA filters into the cleanroom. Because this type of cleanroom is sealed, the forceful entry of air creates pressure higher than that of surrounding rooms. This reduces the possibility for particles to enter the room, as the only air entering the room is forced through filtration. The number of complete air changes per hour is measured, and the higher the rate, the higher the cleanroom rating. Positive pressure, hardwall cleanrooms also offer greater control over air conditions such as humidity and temperature.

Negative Pressure

A negative pressure cleanroom is designed to keep what is in the air within the cleanroom from entering the outside world. This is necessary when possible contaminants are being worked with. Internal air is HEPA filtered before removal into the outside environment.

Positive and Negative pressure rooms are typically used in conjunction, depending on the process flow and what is being manufactured or produced. Utilizing both types of cleanroom can keep specific conditions in specific rooms.

Clean Air Classification
(0.5 um particles/ft3)
ISO Designation > 0.5 um particles/m3 Microbiological Active Air Action Levels
Microbiological Settling Plates Action Levels
(diam. 90mm; cfu/4 hours)
100 5 3,520 1e 1e
1,000 6 35,200 7 3
10,000 7 352,000 10 5
100,000 8 3,520,000 100 50

Components of a Clean Area

Critical Area

The critical area is the area where final sterile product must be exposed to environmental conditions and maintain sterility. The product is vulnerable in this stage and will not be sterilized upon packaging, so it cannot become contaminated in this environment. This area has the highest ISO classification – Class 100 (ISO 5). This means that particulates & microbiological levels in the air must be the lowest as not to contaminate the sterile product. The room requires HEPA filtered, high-velocity air flow.

Supporting Clean Area

Areas that are considered supporting areas to the cleanroom are where to-be-sterilized products are held, transferred, or in-process. Supporting clean areas typically surround the critical area. Air flow must go from areas of higher cleanliness requirements to lower (aka “critical areas” have positive air pressure compared to supporting clean areas).

Required Measurements in a Cleanroom

Air Filtration is necessary for clean environments, and depends on classification level.

Cleanroom Design

Cleanroom design must optimize personnel & material flow to limit the chance of contamination. This includes incorporating an “Ergonomic” layout of equipment & workstations that is designed to limit number of transfers or entries to reduce chance of contamination (i.e. card access to rooms). Cleanrooms often employ security controlled air locks with specific air flow & pressure monitoring often necessary. HVAC monitoring and documenting (data trending) is essential to ensure that all components of the clean environment system are working as they should. Many of the monitoring and clean systems are dependent on HVAC, such as air pressure, air filtration, and the monitoring thereof.

Cleanroom Planned Maintenance

Planned maintenance of the controls, HVAC systems, and monitoring systems is required and essential to maintain the integrity of clean environments such as clean rooms.

Malfunctions or loss of “clean room” status (as indicated by monitoring systems) can shut down production, contaminate inventory and in-process product, and cause massive financial and time delays. Planned maintenance is essential to prevent unnecessary shut downs and avoid possible accidental loss of product or contamination.

Cleanroom Qualification Studies

The following measurements are taken in qualification studies for cleanrooms to determine the classification level:

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