What Is a Cleanroom?
A cleanroom is a room in which the number of airborne particles is continuously monitored, along with temperature, humidity, and pressure. In Poland, it is known as a “clean room,” and both terms—the Polish and the English—mean exactly the same thing and can be used interchangeably. What distinguishes a cleanroom from an ordinary production room is not its appearance, but the way it is designed and operated. Walls, ceilings, and floors are made of smooth, non-dust-generating materials that are easy to clean and resistant to disinfectants. Air enters the room through a filtration system, in which HEPA filters play a key role by capturing various fractions of contaminants before the air even enters the room. People enter the room through personnel airlocks, while raw materials and supplies are brought in through material airlocks, also known as pass-through windows. The number of these airlocks and how they operate depend on the required cleanliness class. It’s worth clearing up one common misconception right away. A cleanroom is not simply a very thoroughly cleaned room. Visual cleanliness and cleanliness as defined by cleanroom standards are two completely different things, because even a room that looks spotless may not meet the required class if there are too many particles floating in the air that are invisible to the naked eye.
What are cleanrooms used for?
Cleanrooms are used in environments where even the slightest contamination can destroy a product or skew test results. They are most commonly found in the industries listed below. In the pharmaceutical and biotechnology industries, cleanrooms are essential for the manufacture of sterile products, such as injectable drugs and vaccines, where every particle or microorganism in the air poses a direct threat to the patient. In the electronics industry, particularly in semiconductor manufacturing, a single microscopic particle settling on a silicon wafer can damage an entire integrated circuit; therefore, this sector adheres to some of the most stringent cleanliness classes in existence. In the production of medical devices, environmental cleanliness directly translates to patient safety, especially for devices that are implanted or come into direct contact with tissues. In the cosmetics and food industries, the requirements are generally less stringent but still significant, as a controlled environment protects the product from microbial contamination during filling or packaging.
Cleanroom classes according to ISO 14644
The primary document governing the classification of cleanrooms is the ISO 14644-1 standard, implemented in Poland as PN-EN ISO 14644-1. The standard defines nine cleanliness classes, ranging from ISO 1—the most stringent environment—to ISO 9, which in practice corresponds to the air quality of a typical office room. The classification is based on counting how many particles of a specific size may be present in one cubic meter of air. The lower the class number, the fewer particles are allowed, and thus the cleaner the air must be. For comparison, ISO Class 5 allows a maximum of 3,520 particles measuring 0.5 micrometers per cubic meter of air, while ISO Class 7 allows as many as 352,000—that is, 100 times more. This difference clearly illustrates how demanding the higher cleanliness classes are and why maintaining them requires advanced ventilation and constant monitoring. The standard also stipulates that classification is performed separately for three states of the room. The “as-built” state refers to a room that is technically complete but without equipment or personnel. The “at rest” state covers a room with installed and operational equipment but without people inside. The “in operation” state is the most demanding situation, as it accounts for the normal operation of personnel and equipment—and thus the greatest risk of introducing contaminants.
Classes A, B, C, and D in the pharmaceutical industry
In addition to the ISO classification, the pharmaceutical industry uses a parallel system of GMP classes, designated by the letters A, B, C, and D, as described in Annex 1 to the EU Guidelines on Good Manufacturing Practice. In Poland, these requirements are established by the Regulation of the Minister of Health dated November 9, 2015, on Good Manufacturing Practice requirements, whose Annex 1 has been thoroughly amended and will take effect in its new form on December 18, 2024. Classes A and B correspond to ISO Class 5 at rest and cover the most critical areas, such as the sterile product filling area. Class C corresponds to ISO Class 7, and Class D to ISO Class 8; these two classes are used for less critical stages of sterile product manufacturing or as the surrounding environment for isolators. The revised Annex 1 places significantly greater emphasis on contamination risk management than its previous version, which in practice means more documented decisions and justifications on the part of the manufacturer, not just compliance with particle count limits.
What makes up a cleanroom?
Behind each cleanliness class lies a specific technical infrastructure. The ventilation and filtration system, based on HEPA filters—and, in the highest classes, also ULPA filters—is responsible for supplying air of the appropriate purity and for exchanging it multiple times per hour. The effectiveness of such filters is regulated by the EN 1822 standard, later supplemented by the ISO 29463 standard, and it is these standards that define the filtration efficiency classes. An H13-class filter must capture at least 99.95 percent of the hardest-to-capture particles, while an H14-class filter—most commonly found in cleanrooms with the highest cleanliness classes—must capture at least 99.995 percent of such particles. Where requirements are even more stringent—for example, in microelectronics—ULPA filters of classes U15 through U17 are used, with efficiency levels reaching several decimal places.
The pressure difference between rooms—typically positive pressure in cleaner zones relative to less clean ones—prevents contaminants from entering through leaks and open doors. Personnel and material airlocks enforce a controlled entry route for people and raw materials, often combined with changing into protective clothing. Finishing materials are selected so that they do not generate their own particles and can withstand frequent chemical disinfection. In many modern facilities, this entire infrastructure is overseen by a BMS (Building Management System), which integrates control of ventilation, filtration, and electrical systems in a single location and allows for a rapid response if any of the parameters begin to deviate from the norm.
How is a cleanroom managed on a day-to-day basis?
Designing and building a room to meet the required class is just the beginning. The classification confirmed during acceptance testing indicates that the room is capable of meeting the standard at that specific moment, but it says nothing about how it is operated on a day-to-day basis, who enters it and when, what condition the room is in at any given moment, or whether it has been properly cleared after cleaning or quality control. This is no longer a matter of construction, but of daily management of the room’s status and documenting every change in a way that will stand up to a future audit. We discuss this very topic—the practical aspects of cleanroom operation and how digital tools are replacing paper documentation at the room’s entrance—in greater detail on our website.
Summary
A cleanroom is a space with strictly controlled air parameters, designed in accordance with ISO 14644 and, in the case of the pharmaceutical industry, additionally in accordance with Good Manufacturing Practice requirements. The cleanliness class that must be achieved depends on the industry and on how sensitive a given manufacturing process is to contamination. However, classification and construction alone are not sufficient to maintain compliance throughout the room’s entire lifecycle. Before the room can even enter routine operation, it must undergo a qualification process, described in the article “From Technical Acceptance to First Production.” We discuss what the day-to-day operation of a cleanroom actually entails, the risks associated with manual documentation, and how digitization is changing the landscape in our next article, “What Day-to-Day Cleanroom Operations Look Like.”
Sources:
- Norma PN-EN ISO 14644-1:2016 (zgodna z EN ISO 14644-1:2015);
- Norma EN 1822:2009 oraz ISO 29463:2011;
- Rozporządzenie Ministra Zdrowia z dnia 9 listopada 2015 r. w sprawie wymagań Dobrej Praktyki Wytwarzania (Dz.U. 2015 poz. 1979, z późn. zm.), Załącznik nr 5, Aneks 1, w brzmieniu obowiązującym od 18 grudnia 2024 r.
