Long associated with the pharmaceutical and microelectronics industries, cleanrooms are now used in sectors ranging from healthcare and space to cosmetics and food production. But beyond ISO classifications, filtration systems and strict procedures, a new generation of controlled environments is emerging: more modular, more intelligent and increasingly capable of adapting their operation to actual risk.

At first glance, a cleanroom might simply appear to be a particularly well-filtered room.

In reality, it is a complete system in which every element matters: outdoor air quality, filtration, pressure, materials, equipment, movement of people, cleaning procedures, operator behaviour and workflow organisation.

Most importantly, the contamination being controlled is, in the vast majority of cases, invisible.

Three main categories of contaminants must be considered in a controlled environment.

The first is particulate contamination, including dust and inert airborne particles.

The second is microbiological contamination: bacteria, fungi, yeasts, moulds and viruses.

The third is chemical or molecular contamination, which may originate from atmospheric pollution, materials, industrial processes or human activity.

One of the main challenges lies in their size.

A human hair is approximately 100 micrometres in diameter, while the human eye struggles to distinguish particles smaller than around 50 micrometres. Yet many of the contaminants monitored in cleanrooms are far below this threshold.

Some respiratory viruses can be as small as approximately 0.1 micrometres.

Contamination control therefore largely means managing an environment that our senses cannot directly observe.

Even with highly efficient air-treatment systems, one factor remains particularly difficult to eliminate: people.

Even a relatively still person can generate a significant number of particles. As soon as they move, particle generation increases through the resuspension of particles from clothing, hair and skin.

The human body also continuously sheds skin cells.

In a cleanroom, protective clothing therefore acts as a genuine barrier between the operator and the controlled environment.

Coveralls, masks, gloves, hair covers and overshoes are selected according to the level of risk and the classification of the area.

But protective equipment alone is not enough.

The way operators move, their hygiene, the procedures they follow and the objects they bring into the room all directly influence contamination levels.

A smartphone, laptop or even a pair of glasses can become a contamination vector if it is not included in appropriate contamination-control procedures.

Not all cleanrooms operate according to the same principles.

In some applications, the objective is to protect what is inside the room.

A pharmaceutical production area, for example, may be maintained under positive pressure so that air tends to flow outwards. This creates an aerodynamic barrier against external contaminants when an opening occurs.

In a laboratory handling a hazardous biological agent, the logic is reversed.

This time, the contaminant must be prevented from escaping.

The environment is therefore maintained under negative pressure, causing air to flow inwards.

This difference illustrates a fundamental principle in controlled-environment design: before selecting a technical solution, it is essential to determine exactly what needs to be protected and from which risk.

The HVAC system — heating, ventilation and air conditioning — is at the technical heart of a cleanroom.

Outdoor air is drawn in, filtered and treated to control parameters such as temperature, humidity, airflow and particle concentration.

Depending on the risk, an installation may operate with 100% fresh air or recirculate part of the treated air.

However, having an efficient system does not automatically guarantee uniform protection.

A poorly positioned extraction vent, a trolley placed in front of an air return or a piece of equipment disrupting airflow can create areas with poorer ventilation.

As a result, a room can comply with its overall regulatory criteria without providing exactly the same level of control throughout its entire volume.

This is precisely one of the issues on which current research is focusing.

To truly understand how a contaminant behaves, measuring its concentration is no longer enough.

We also need to know where it goes.

Fluid mechanics and computational modelling can now be used to simulate air movement within controlled environments.

These tools can help map airflow patterns, identify dead zones, optimise the position of air supply and extraction points, and determine the most effective location for an air purification system.

Because even a highly efficient air purifier may perform far below expectations if it is installed in the wrong place.

This approach becomes particularly valuable when combined with microbiology.

Viruses remain one of the most complex challenges in microbiological air control.

Traditional simulation models generally represent physical particles or gases.

A bioaerosol, however, is considerably more complex.

It can consist of a mixture of biological fluids, particles, bacteria or viruses whose characteristics evolve over time.

The question is therefore not only where a particle travels, but also how long the biological agent it carries remains infectious.

Current research is seeking to incorporate these biological parameters into fluid-mechanics models.

The objective is to simulate not only the movement of a bioaerosol, but also how the associated infectious risk evolves over time.

This approach also relies on experimentation.

Test facilities can now generate atmospheres contaminated with real microorganisms to assess air-treatment technologies under conditions closer to their actual use.

A 30 m³ experimental test chamber presented during the session can be used with bacteria, viruses and moulds while controlling temperature, humidity and airflow.

This makes it possible to go beyond the performance figures provided by manufacturers.

Two technologies both marketed as "air purifiers" can, in practice, deliver very different levels of efficiency.

And once again, the intrinsic performance of the device represents only part of the equation: its position within the room also plays a major role.

Another important development concerns the way controlled environments are built.

Historically, creating a cleanroom often involved constructing a heavy, expensive and relatively fixed infrastructure.

New modular solutions now make it possible to design contained environments that can evolve according to changing requirements.

Containment laboratories can, for example, be built from modules, expanded, adapted or potentially deployed in different geographical contexts.

This modularity creates new possibilities for research, production and situations requiring the rapid deployment of additional capacity.

However, the same requirements for containment, air treatment and contamination control still apply.

Modular does not mean less demanding. It means designing differently.

Simulation is also paving the way for an even more ambitious development: the digital twin.

The principle is to create an accurate virtual representation of a real environment, such as a cleanroom, production area, hospital room or operating theatre.

This digital replica could be continuously supplied with data from sensors installed in the physical environment.

Information on airflow, temperature, humidity, particle concentration and, eventually, biological contaminants could then be incorporated into the model.

The aim would be to adapt the operation of the facility in real time.

If contamination were detected in a specific area, the system could, for example, modify the air-handling parameters or adjust an air-purification device.

The cleanroom would no longer simply be a controlled environment.

It would gradually become an environment capable of responding to its own conditions.

Achieving this type of dynamic management will require another technological development: systems capable of rapidly identifying infectious microorganisms in the air.

Today, several environmental parameters can already be monitored continuously.

CO₂, for example, can provide useful information about ventilation and air movement. But it is not, on its own, a direct indicator of infectious risk.

One area of research is therefore the development of biosensors capable of detecting and signalling the presence of infectious bacteria or viruses in real time.

Combined with digital models and air-treatment systems, such sensors could significantly transform the monitoring of controlled environments.

These technological developments also address another urgent issue: energy consumption.

Cleanrooms are particularly energy-intensive. Ventilating, filtering, heating, cooling and maintaining pressure differentials require significant amounts of energy, sometimes even when facilities are not in use.

For many years, the dominant approach was to oversize installations: greater airflow, higher air-change rates and more power provided an additional safety margin.

Today, the focus is increasingly shifting towards matching performance to actual needs.

An operating theatre that is not used overnight, for example, could operate in a reduced or standby mode, provided that contamination remains under control and nominal performance can be restored before the room is used again.

In some industrial environments, this type of optimisation could lead to substantial energy savings.

The challenge is therefore no longer to choose between environmental performance and health protection.

The cleanroom of the future will need to be both safe and energy-smart.

Contamination control is gradually entering a new phase.

Alongside established standards, filtration systems and procedures, new tools are emerging: modelling, fluid mechanics, bioaerosol research, modular construction, sensors and digital twins.

These developments do not replace the fundamental principles of cleanroom design.

On the contrary, they could help apply them with greater precision.

Because the objective is no longer necessarily to create the most powerful installation possible, but rather the environment best suited to the actual level of risk.

This evolution could help laboratories reconcile three requirements that have long been difficult to combine: contamination control, flexibility and energy efficiency.

Article based on the session dedicated to contamination control, cleanrooms and new approaches to modelling and monitoring, presented by ASPEC at Forum LABO.