Many industries depend on cleanrooms, which are constructed to specific international standards, to manufacture products free of dirt and bacterial contamination.

Cleanrooms particularly benefit industries involving food processing and the manufacture of pharmaceuticals, chemicals, electronics, aircraft, and missile equipment, and they also appear in research laboratories, testing facilities, and other environments that require sterile conditions.

The type and capacity of work that occur in cleanrooms govern the standards under which they’re built. Environmental conditions including heat loads (the energy needed to keep the room at a certain temperature), temperature, pressure, and humidity controls factor into proper cleanroom construction.

Today’s industrial cleanrooms must adhere to stringent standards to control contaminants and particulate matter. These standards vary by industry and are compiled below.

At a glance:

Clean Room Requirements and Specifications

Considerations for Cleanroom Construction and Design

How to Build a Cleanroom

Clean Room Requirements and Specifications

Ultimately, three characteristics define cleanrooms:

Internal surface and equipment cleanliness inside the cleanroom—all surfaces should be “smooth and impervious,” easy to clean, and kept free of contamination

Maintenance of airflow quality, usually at controlled temperature and humidity levels

The strict control of staff allowed access to the cleanroom

ISO 14644 1 Cleanroom Standards

Cleanrooms must adhere to the ISO 14644-1:2015 Parts 1 and 2 standards. These evolved from the Federal Standard FED-STD-209 E, which is currently being phased out. ISO 14644 1 standards classify a cleanroom according to how clean its air is, as measured by the number of particles per cubic meter. There are nine different levels of cleanliness, as shown in the chart below. Each level is ten times the difference from the levels before and after it. The standards range from the particle contamination you’d find in a city outdoors as ISO 9 to the cleanest level of cleanroom, ISO 1. Under the older federal 209E standard, each class number represents the number of particles per cubic foot, so that a Class 100 cleanroom would have 100 particles or fewer contained in that area.

Calculating Clean Room Air Changes per Hour (ACR)

Airflow, commonly referred to as Air Change Rate or ACR, is the key ingredient to keeping a clean room at the level of cleanliness it’s supposed to be. While a standard air conditioner will circulate the air in a room between twice an hour and once every two hours, air changes in cleanrooms must be more frequent. The cleaner the room, the more air changes there should be and the more flow devices should be mounted on the ceiling.

Although there are tables showing recommended airflow rates for each type of cleanroom, there is a lot of variety in the numbers. That’s because pinning down airflow rates is complicated, depending on factors like the specific cleanroom’s height and the activities it will host.

To calculate the airflow rate, it’s crucial to consider whether the airflow is laminar (unidirectional) or turbulent (mixed or in multiple directions). For turbulent conditions, in ISO 6-9 clean rooms, you can use the following equation, where CFM stands for cubic feet per minute:

CFM x 60 / room volume = air changes per hour

Turbulent and mixed airflow can’t be used for higher rated cleanrooms, since the air flows unevenly, creating pockets in which contaminants can get trapped.  For clean rooms with laminar flow, air velocity sampling must be done to find the ACR. The high and low ends of the average air velocity scale are laid out in the ISO guidelines: cleanrooms at levels 2, 3, 4, and 5 all should have an average air velocity maximum at half a meter per second. Low end air velocity for an ISO 5 cleanroom is .2 meters per second, but ISO 2, 3, and 4 cleanrooms have a .3 meter per second minimum. In laminar cleanrooms, blowers are usually set in the ceiling or inside hoods, while air returns are generally placed around the bottoms of the room’s walls. It’s important to remember that laminar rooms should have airflow at an angle at least 18 degrees away from straight down to ensure the air sweeps contaminants off surfaces.

ISO recently added a further 11 parts to their regulations. All of these outline the requirements for the construction and the operation of cleanrooms as well as various practices and procedures used to manage contamination risks.

Considerations for Cleanroom Construction and Design

Cleanrooms protect against airborne particles and regulate humidity, temperature, and pressure. They do so primarily by complex air pressure and filter systems as well as specifically tailored HVAC units. While HEPA (High-Efficiency Particulate Air) filters are generally used to trap particles .3 microns and larger, higher rated cleanrooms will also use ULPA (Ultra Low Particulate Air) filters to catch smaller contaminants. Some considerations for cleanroom design and construction include:

Cleanliness levels required in one or more locations—sometimes facilities require multiple rooms with different cleanliness levels

Floor layouts that optimize the manufacturing process or processes taking place in cleanrooms, including identification of critical work areas

Identification of HEPA filter locations for unidirectional laminar airflow, or ULPA filters for multidirectional turbulent airflow and analysis of how these will affect airflow patterns

Requirements for electronic communications and process piping

Additionally, cleanrooms must control environmental conditions, including temperature, humidity, pressure, static buildup, and ventilation. Designers must also anticipate potential future changes to these conditions. Environmental considerations include:

How HVAC design will meet the tight environmental specifications of the cleanroom

Monitors, network connections, and other equipment needed to control required elements

Management of heat loads resulting from equipment use and personnel movement

Some additional points to remember when designing a cleanroom facility:

The cleanliness of a cleanroom is not static. Adding equipment and workers can change a cleanroom that was previously ISO 4 to an ISO 5 level.

For situations in which multiple cleanrooms are joined together, the cleanest room should be kept under the highest positive pressure to blow out potential contaminants from lower level cleanrooms that open onto it.

Connecting spaces should have no more than two ISO levels of difference to avoid lowering the cleanliness of the cleaner room. Spaces between should also have a differential air pressure of .03-.05 inches water gauge, but the air pressure becomes more difficult to control and more expensive to maintain as it gets higher.

The cleanest room in a group of cleanrooms should only have one entrance to keep employees from using it as a pathway to less clean rooms, increasing its contamination.

How to Build a Cleanroom

Cleanrooms must be constructed in stages, starting from standard construction of walls and infrastructure to progressively cleaner construction activities to make the finished room as clean as possible.

Stages of the Cleanroom Design and Construction Process

Cleanroom assembly typically involves four stages, each with specific protocols.

Stage 0: Regular construction

During regular construction, workers build the surrounding facility in which the cleanroom will be constructed.

Stage 1: Clean Construction

Clean construction involves working with the end user to create a utility matrix (UM) containing detailed specifications for every piece of equipment intended for the cleanroom.

The UM is instrumental in ensuring that all equipment integrates appropriately with each other, particularly the HVAC system. Workers will consult the UM throughout the rest of the construction process.

Stage 2: Pre-Cleanroom Construction

Before initiating this stage, workers create a “smock room” with airlocks and air cleaners to facilitate clean entry and exit to and from the job site. Workers must wear booties and protective equipment at all times, and HEPA filters should be installed to mitigate dust buildup resulting from cutting and drilling activities.

During pre-cleanroom construction, workers build within this sterile environment the outer components of the cleanroom.

Stage 3: Active Cleanroom

After constructing the external elements of the cleanroom, workers complete punching and finishing details within the cleanroom. During this phase, workers must adhere to the cleanroom’s required cleanliness protocols.

Kwang Cleanroom is proud to offer examples of a variety of our cleanroom projects below. Electronics Assembly Cleanrooms, Cosmetic Production Cleanrooms, Automotive Cleanrooms, Aerospace Cleanrooms, Medical Device Cleanrooms, Pharmaceutical & Biotechnology Cleanrooms, Powder Coating Cleanrooms.

Call us with any questions you have or to place an order!