When we hear the term “cleanrooms,” we immediately associate it with hospital operating rooms, pharmaceutical and bioanalysis laboratories, and the nuclear industry in general, although nowadays they are not exclusive to these areas. The truth is that this concept emerged and began to formalize in the late 19th century. During that time, several surgeons and microbiologists observed the benefits of proper ventilation in their workspaces. They noticed a significant decrease in the infections that used to occur in these areas. Therefore, we could say that from the very moment these places started to be referred to with the term at hand, the concern to establish the conditions that should be met for achieving proper cleanroom cooling began.
Basic concepts relevant to cleanroom cooling
Essentially, a cleanroom, or sterile room, is a controlled environment designed with the purpose of conducting operations and processes with the least possible tolerance for contamination. In this way, it is possible to guarantee the safety and quality of a procedure (such as surgery) or a delicate product (such as medication). Consequently, to achieve the lowest level of contamination in such environments, it is essential to follow a series of carefully controlled environmental guidelines. As we will see later on, these parameters form the basis of cleanroom cooling.
In this sense, the design, construction, and equipment of such a space must take into account the central objective of minimizing and preventing the entry, generation, and retention of any contaminating particles. Understanding that these agents (microbes, viruses, etc.) are capable of altering the results of the procedures carried out within. Whether it is surgical operations, the production of medications, or food processing, among others.
General conditions of cleanrooms
From this perspective, the facilities we are referring to can consist of one or a set of enclosures. Depending on their purpose, certain variables must be maintained within precise limits within each enclosure. These variables include lighting, temperature, relative humidity, air quality, differential pressure, and noise levels. As you can see, many of these variables are related to cleanroom cooling.
In general, based on their purpose, these spaces must have specific conditions for:
- Microbial exclusion, aiming to prevent contamination of sterile materials, raw materials, instruments, components, and surfaces in procedures that require asepsis.
- Microbial limitation in occupied areas near where aseptic processes are performed. In this case, the idea is to minimize the intrusion of contaminating elements into the cleanroom.
- Particle exclusion. Often, this condition is associated with microbial exclusion. However, it also applies individually to pre-washed instruments and materials prior to sterilization.
- Limitation of particle presence, in order to reduce the particle load on materials and instruments prior to washing.
- Prevention of cross-contamination, to minimize contamination between materials and/or products.
- Exclusion of external contamination, including that which can be brought in or generated by the operators themselves.
Sectors that have these spaces and require cleanroom cooling
- Healthcare Sector: Hospitals, clinics, and healthcare facilities. Particularly for areas dedicated to operating rooms, laboratories for analysis, imaging and X-rays, rooms for infected and immunocompromised patients, medical instruments, and more.
- Pharmaceutical Industry: Human and veterinary medicines, cosmetic chemicals, and biotechnological products.
- Food Industry: Precooked or raw meat and vegetable products, sliced, packaged, or canned. Beverages in general.
- Technology: Electronics, microelectronics, nanotechnology, automotive, and aerospace development, among other industries.
- Research, Development, and Innovation (R&D+I): Research laboratories, universities, containment rooms, etc.
Classification influences cleanroom cooling
According to the type of ventilation employed, we can identify two types of cleanrooms:
1. Non-unidirectional airflow: In these cleanrooms, clean, filtered air is supplied from the ceiling through high-efficiency air filters. This clean air mixes with the room air, effectively removing contamination generated by operators, tools, machinery, or other elements. Exhaust systems located at the lower part of a wall are responsible for expelling the contaminated air. This ventilation system is known as “turbulent ventilation.”
2. Unidirectional airflow: These cleanrooms require a higher volume of air compared to the previous type. The design of the cleanroom cooling system in such cases should incorporate a ceiling-mounted air supply that covers the entire area, along with the presence of filters. The airflow velocity is typically set between 0.3 and 0.5 meters per second (m/s) to effectively remove contamination. The air enters through the entire ceiling, passing through the installed filters to eliminate contamination. The contaminated air is then expelled through the floor of the enclosure. It is important to note that this type of installation is more expensive than non-unidirectional ventilation.
The classification of cleanrooms and the type of airflow system chosen greatly influence the design and implementation of cleanroom cooling strategies to ensure the appropriate air quality and contamination control within the controlled environment.
How should cleanroom cooling be?
In summary, the ventilation conditions of cleanrooms depend on the requirements of the processes conducted within them. Generally, the management of cleanroom cooling is guided by four basic criteria:
Temperature
This is one of the elements that vary according to the specific processes carried out in cleanrooms. For example, in a food processing plant, the temperature range might be between 6°C and 10°C, while in a hospital operating room, it should be between 22°C and 26°C. However, in more demanding circumstances, such as specific cardiac surgeries, it may need to be lowered to 17°C.
In any case, it is essential to pay attention to variables such as latent heat, which is generated within the cleanroom due to the operation of the system’s motors, lighting, and presence of people.
Humidity
Regarding this criterion, it is ideal for the air circulating inside cleanrooms to have low humidity levels. This helps to absorb moisture from various sources and prevent condensation on surfaces, which can be a breeding ground for microorganisms.
Referring back to our previous examples, in a food processing plant, an acceptable range of relative humidity would be between 60% and 70%. On the other hand, in an operating room, it should be between 45% and 55%.
Airflow, a relevant factor in cleanroom cooling
In a cleanroom, the circulating air consists of two elements: recirculated air and outside air. The recirculated air should circulate in a lower proportion within the cleanroom to remove moisture, gas concentration, particles, and microorganisms, which will then be expelled through the exhaust system.
For food processing in a cleanroom with a temperature range of 6°C to 10°C, the air volume should be refreshed at a frequency of 20 to 30 air changes per hour (ACH). On the other hand, in an operating room, the ideal air change frequency is 20 ACH, at a velocity between 0.20 and 0.40 m/s.
Below these ranges, it is not feasible to guarantee effective removal of contaminants. Undoubtedly, the supply of outside air is critical to eliminate gas concentration and provide positive pressure.
Filtration
Certainly, another essential objective of cleanroom cooling is to filter the air to prevent the entry of particles and microorganisms. The outside air passes through a system of filters. Then, it goes through HEPA or ULPA filters that further clean and decontaminate the outside air. These filters have different classifications based on their capabilities.
We develop the necessary systems and units to cool cleanrooms
At Intersam, we design and manufacture tailor-made cooling systems for various industrial and commercial applications. With 28 years of experience in the industry, we can take on large-scale and complex projects both in Spain and internationally. Our manufactured units feature cutting-edge technology to ensure high performance and maximum energy efficiency. Additionally, we focus on providing personalized solutions to meet the specific needs of each client.