A cleanroom is an environment specifically designed, constructed, and maintained to control the concentration of airborne particles within a defined volume. The design and management of such spaces aim to minimize the introduction and retention of airborne particulate matter in order to ensure a contaminant-free working environment that is as clean and isolated as possible.
The main characteristics of a cleanroom are:

Air control and filtration.
Air is a carrier of particles—and therefore of dust, microbes, and aerosol suspensions—and represents a potential risk factor in controlled environments. For this reason, it is essential to manage the ventilation system using an HVAC (Heating, Ventilation, and Air Conditioning) system that allows the maintenance of a constant temperature regardless of external climatic variations and reduces the risk of contamination due to humidity. To ensure clean and particle-free air, the ventilation system must also be equipped with suitable filtration using HEPA (High Efficiency Particulate Air) filters, which are designed to capture up to 99.999% of particles larger than 0.3 microns.

Airflow types.
In unidirectional (laminar flow) cleanrooms, filtered air is distributed evenly across the room through parallel lines to avoid particle recirculation and to direct them towards extraction zones. In turbulent flow rooms, on the other hand, air is mixed inside the room, creating a swirling movement. This second type is less expensive to build and maintain, suitable for larger and more complex configurations, but provides a lower cleanliness level (ISO Class 8–9) compared to laminar flow rooms.
Environmental parameter control.
Temperature, humidity, pressure, and airflow velocity must be maintained within precise ranges to ensure stable and safe operating conditions.

Materials and finishes.
Materials used in cleanrooms must be easy to clean, disinfect, and sterilize. Commonly used materials include high-pressure laminate (HPL), PVC, stainless steel, aluminum, epoxy resins, and linoleum.

Gowning and access.
Authorized personnel must wear specific clothing and protective equipment (coveralls, caps, goggles, masks, shoe covers) and follow strict gowning and access procedures to minimize the introduction of contaminants.

Monitoring and control.
The cleanroom is equipped with a continuous monitoring system for environmental parameters and operational conditions, enabling the detection of any anomalies and timely intervention.

The most widely used classification system globally is defined by the ISO 14644-1 standard, which classifies cleanrooms according to air cleanliness—that is, the concentration of particles per cubic meter of air—specifically based on the number of particles larger than 0.5 microns. The cleanest class (ISO 1) has an extremely low particle concentration, while the least clean (ISO 9) has a higher concentration. Measurements are carried out under three different conditions: “as built” (completed environment with no equipment or personnel), “at rest” (equipment installed and operating, but no personnel present), “in operation” (equipment operating and personnel present).
Another classification system, primarily used in the medical and pharmaceutical sectors, is defined by the EU-GMP (Good Manufacturing Practice) Guidelines. This document identifies four classes of cleanrooms, from A to D, and provides recommended limits for airborne particle concentration for each class.

Designing a cleanroom begins with a precise definition of the requirements: the cleanliness class, dimensions, intended use, and applicable regulations. Based on these parameters, suitable materials are selected—resistant to corrosion, easy to clean, and capable of minimizing particle generation. The design then includes the air filtration system, typically with HEPA or ULPA filters, and the ventilation system to ensure proper airflow and air exchange. Electrical, water, and lighting systems are planned according to the specific needs of the cleanroom.

Once the design is finalized, construction begins with site preparation and the installation of walls, floors, and ceilings using cleanroom-compatible materials. Systems for filtration, ventilation, lighting, and environmental control are then installed, and all joints are carefully sealed to prevent leaks and contamination.

After construction, the cleanroom undergoes validation through measurements of particle concentration, temperature, humidity, and differential pressure. Filter integrity is tested, and, if all standards are met, certification is issued. Finally, qualification ensures that both operators and processes comply with required safety and quality standards, completing the process that guarantees a fully functional and compliant cleanroom.