EOLIOS's in-depth study made it possible to determine the airflows in the cleanroom in order to verify its cleanliness, in accordance with the ISO 14644 standards.
A cleanroom is a highly controlled space, designed for applications such as scientific research, manufacturing, electronics, pharmaceuticals and aerospace. Its main objective: to maintain an extremely high level of cleanliness by rigorously controlling the concentration of airborne particles. Other essential parameters — temperature, humidity, pressure — are also closely monitored and regulated.
The essentials. For Dalkia (IPSEN site), EOLIOS modelled the airflow of a cleanroom by CFD to check its ISO 14644 compliance. The study maps air velocities and temperatures around the machines, checks the laminar flow, the sizing of the deflectors and the flow rates of the FFU and AHU supplies, to guarantee a sweep with no stagnation zone where contamination would build up.
To ensure compliance with the standards, cleanrooms are equipped with advanced air-filtration and airflow-control systems, smooth and easy-to-clean surfaces, and rigorous staff entry and exit procedures (suits, gloves, masks, shoe covers).
The cleanliness standards guarantee a precise level of purity in terms of the concentration of airborne particles. The most commonly used standard is ISO 14644, which establishes cleanliness levels according to the number of particles per unit volume of air — from ISO 1 (the cleanest) to ISO 9 (the least clean). When a cleanroom is designed and used, rigorous maintenance, cleaning and monitoring procedures are put in place to constantly maintain the required levels.
ISO 14644 classifies the particulate cleanliness of a cleanroom by the number of particles per m³ of air, from class ISO 1 (the cleanest) to ISO 9. The target class sets the filtered-air flow rates and the renewal frequency to hold.
Several means make it possible to limit contamination. The presence of a laminar flow ensures a linear, turbulence-free flow of air, in a single direction. It is also necessary to limit the airflows rising from the floor towards the breathing zones, which can contaminate products, processes and users.
The use of deflectors is fundamental: well sized, these air deflectors ensure a more precise airflow while improving air quality. Their objective: to minimise the dispersion of particles and contaminants in the ambient air.
A laminar flow is a regular, unidirectional, turbulence-free air movement, generally directed from the ceiling towards the floor. It carries the particles towards the low extracts instead of letting them recirculate towards the sensitive zones.
Before the simulation, all the supply / extract systems must be identified and their flow rates recorded in order to model them correctly.
The fan filter units (FFU), installed in grilles or in the ceiling, blow a filtered airflow through their integrated filter. The fan creates a positive pressure that pushes the filtered air into the room and prevents external contaminants from entering.
An FFU is a fan-plus-HEPA-filter module integrated into the ceiling. It blows filtered air in slight positive pressure, which pushes contaminants outwards and prevents unfiltered air from entering.
The AHU (Air Handling Unit) filter supply is a ventilation and conditioning system providing distribution, filtration, heating, air conditioning and humidity control — to improve the indoor air quality and maintain comfort conditions.
The AHU extracts collect and recycle the contaminated air (particles, pollutants, odours) to bring it back to the AHU, where it is filtered and conditioned before being redistributed through ducts and grilles, ensuring a uniform ventilation.
The laminar-flow extract maintains a high level of cleanliness and a precise control of the particles, creating a unidirectional and regular air current, generally directed from the ceiling towards the floor.
CFD simulation plays an important role in the cleanliness of cleanrooms: it provides an in-depth understanding of the air movement, the distribution of particles and the dispersion of contaminants. Air-velocity and air-temperature studies are carried out in the hall to determine whether the flow rates are adequate and whether the ventilation systems allow the extraction of pollutants.
EOLIOS models the airflow in a cleanroom taking into account the ventilation systems, the filters and the equipment. We thus guarantee an adequate air flow rate and a homogeneous distribution to minimise the stagnation zones where contamination could accumulate. By studying the airflows, the hot spots and the recirculation zones, we determine the critical zones; the effectiveness of the filters is also assessed by simulating the filtration of the particles and identifying the leaks of contaminated air.
Our team is consequently able to validate or not the performance of the ventilation systems present, and to ensure that the required cleanliness levels will be reached and maintained in accordance with the specified standards.
Key takeaway. On a cleanroom, it is not the total flow rate that matters but the uniformity of the sweep: a single stagnation zone, however small, is enough to make the ISO class drop locally. CFD is what flushes it out before qualification.
ISO 14644 cleanliness, laminar flow and the supply systems of a cleanroom.
It visualises the air movement, the particle distribution and the recirculation zones, and checks that the flow rates and deflectors ensure a homogeneous sweep. Cleanliness is thus validated before qualification. A related challenge was addressed on our pharmaceutical laboratory, dust project.
It sets the maximum number of particles per m³ of air, from ISO 1 (the cleanest) to ISO 9. The target class determines the filtered-air flow rates and the renewal frequency to maintain in operation.
A unidirectional flow from the ceiling to the floor carries the particles towards the low extracts without letting them recirculate towards the products or the operators. Any turbulence breaks this regular removal.
The FFU filters the air locally at the ceiling and creates a positive pressure; the AHU (air handling unit) treats, filters and conditions the air at building scale before distributing it through ducts. The two are often combined.
By cross-referencing air velocities, hot spots and recirculation zones: where the air stagnates, particles accumulate. CFD locates these critical zones to adjust deflectors, flow rates and extract placement.
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CFD simulation makes it possible to visualise the thermal effects of an analysis machine and the airflows in the cleanroom, in order to verify the cleanliness and performance of the ventilation systems. By modelling air movement, particle distribution and hot spots, EOLIOS validates the achievement and maintenance of the required cleanliness levels.
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