CO₂ Footprint in Cleanroom Technology

Flow pattern of a turbulence-free flow under the influence of the intake point

Influence of an exhaust air intake on the laminar flow in the room

CO₂ Footprint - Factors Influencing in a Cleanroom

Principle diagram of the cleanroom concept with pressure plenum and recirculation modules

Detailed recording of the kinetic energy fields below the waste disposal facility, unaffected or freed from laminar flow.

During times of economic prosperity and unlimited goods traffic, awareness regarding our environment is not particularly pronounced. Now, international crises starkly highlight our self-created dependence, yet we largely ignore the consequences of climate change. Additionally, high energy and operating costs pose significant challenges to industry, especially in cleanroom technology.

It is time to adopt new values. Environment, energy, safety, and sustainability have top priority, and European and regional legislation currently imposes strict regulations concerning sustainable, environmentally friendly processes.

The CO2 footprint is a measure of the total amount of carbon dioxide emissions caused directly and indirectly by activities or generated during the life stages of a product. The product's carbon footprint (Product Carbon Footprint) shows in which phase of the lifecycle significant CO2 emissions occur and how these can be reduced cost-effectively. From raw material extraction through transportation, production, use, and end-of-life scenarios, everything is examined.
To calculate the carbon footprint of products, ISO 14067 is applied.

Emitted greenhouse gases within a product system are recorded and converted into CO2 equivalents to quantify the potential contribution of this product to global warming. Modern measurement technology allows for minimizing measurement tolerances and ensuring a consistent airflow velocity. Practical tests prove that the cleanroom quality is not compromised at reduced airflow velocities of 0.36 m/s. Simulations, innovative cleanroom designs, reliable testing, and thorough risk assessments often justify airflow velocities below the 20% regulation.

"We need courage to change and the willingness for genuine cooperation – to develop solutions together and take responsibility" - Josef Ortner

Airflow velocity HEPA filter

The DIN EN ISO 14644 specifies an airflow velocity at the outlet of HEPA filters of 0.45 m/s ±20% for low-turbulence airflow. This requirement was established decades ago and is partly based on the filtration efficiency of the filter quality at that time. This specification results in enormous air volumes when covering large filter areas or using larger filters. Additionally, there is increased air resistance in the filter environment of approximately 200 – 500 Pascals, caused by the filter resistance and upstream airflow-directing components. These values do not include the system values of ventilation and air conditioning units. Total resistance in ventilation systems typically ranges between 800 and 1000 Pascals. This entails high drive energy, high cooling capacity, bulky ductwork, and large installation components. Modern filter technology enables air velocities well below the standard values without compromising quality. Resistance values decrease significantly, and service life increases manifold. Using resistance-minimized PTFE HEPA filters further enhances this effect. In many cases, cleanroom systems can operate at reduced airflow velocities, leading to investment and operating cost reductions of up to 50%.

Airflow velocity for isolators

The DIN EN ISO 14644 or GMP guidelines specify a uniform airflow velocity of 0.45 m/s ±20% across the entire surface for Class A cleanrooms. The requirement for uniform airflow is generally justified, but it can also be achieved at velocities significantly below the specified values. Always consider possible disruptive external influences that could impair piston airflow. These guidelines must also be adhered to in isolators, which is worth questioning. Isolators are high-density safety systems typically equipped with sterilization or decontamination techniques. Before each process, the entire interior is brought to a 100% germ-free state. External contamination is certainly excluded. Uniform airflow across the entire surface does not necessarily increase safety; in fact, it can have negative effects. Flow simulations and visualizations demonstrate that piston airflow does not guarantee free ventilation in niches or hidden areas. Turbulent airflow is often more effective. Changing the airflow technique from low-turbulence to turbulent simplifies technology and construction significantly. Due to small chamber volumes, air change rates >400 times are easily achievable. (Example: 4 glove isolator, chamber base area 2m x 0.8m = approx. 2600 m³/h with low-turbulence airflow versus approx. 800 m³/h with turbulent airflow, air change rate 600 times). The term "turbulent airflow" does not refer to highly turbulent flow. It should also be noted that the airflow characteristics, especially piston airflow, depend heavily on the suction points and the exhaust system. The exhaust air significantly influences the airflow pattern. The effects of operational interventions, working methods, materials, containers, and technical equipment that negatively impact low-turbulence airflow must not be overlooked.

Outside air, exhaust air, and recirculation

Most systems and devices in the medical and pharmaceutical environment operate as pure exhaust air systems or at least as mixed-air systems with a certain exhaust air component. The justification is usually based on manufacturer specifications and risk assessments regarding contamination spread into the work environment. Exhaust air necessarily includes outside air, which must be conditioned for cleanroom requirements. Regardless of installation effort and space requirements, outside air treatment involves heating, cooling, humidification, dehumidification, and the entire range of filter technology. When examining "manufacturer specifications," it becomes clear that manufacturers assess various risks and add safety margins. This is not a criticism but an encouragement to conduct an independent risk assessment. This topic is particularly relevant to microelectronics, as thousands of production facilities are needed to manufacture microchips. The process exhaust air from process equipment is usually chemically contaminated and must be treated via absorption or adsorption systems.

Three practical examples:

1. In a comparison of measurement data from systems of the same type and manufacturing processes, significant differences in exhaust air volumes were observed. In a coordinated approach with production, all systems were gradually adjusted to match the lowest value. The result was an exhaust air reduction at the site of about 18,000 m³/h = approximately 160 million m³ annually. This also means 160 million m³ of outside air that does not need to be conditioned.

2. For the installation of a process system, the specified ventilation system was set up. During commissioning, without informing the operator and commissioning team, the process exhaust air was pre-set to about 60% of the manufacturer’s specifications, expecting adjustments if issues arose with the product or during startup. The result was that the set values were not changed, and no quality problems occurred.

3. In the 1980s, a state-of-the-art microchip factory was built. One innovation involved the pressure plenum technology and full-surface filtration for about 1000 m² of production area. To ensure the airflow requirements of 0.45 m/s, recirculation systems with a capacity of approximately 1.6 million m³/h were installed. With a room height of 3m, this resulted in about 600 air changes per hour. Despite strong concerns about reducing air volume, the airflow velocity was gradually lowered to 0.3 m/s, accompanied by extensive quality controls. The result was a reduction of about 1 million m³/h in airflow, leading to a significant decrease in system resistance, which in turn resulted in energy and cooling power savings of approximately 7.7 million kWh/year.

These simple examples aim to encourage starting commissioning from a lower value to achieve optimal operating conditions.

Systems in recirculation mode

The technological developments of recent decades have introduced many innovations and improvements. Modern air filtration technology and techniques for treating contaminated exhaust air have enabled many cleanroom and process systems to operate as infrastructure-independent recirculation systems. This allows for reductions in air volumes in simple material transfer systems of about 0.7 million m³/year, decontamination material sluices of about 4 million m³/year, or isolators of about 2 to 6 million m³/year. Additionally, the air handling infrastructure is eliminated.