Variable Air Flow for Cleanrooms as Published in Cleanrooms Magazine

Cleanrooms Magazine has published multiple articles on this subject.  Here are excerpts and links.


Interview with Grant Merrill, Chief Commercial Officer at AES Clean Technology

Discussing dynamic air control with variable air change rates as one way to improve sustainability, Merrill seems cautious but optimistic. Calling the solution both “elegant” and “complex”, he says that though it is not yet mainstream, it is only a matter of time. 

“[Variable air change rates] rely on real-time monitoring of particle counts and the ability of the automation system to make minute-by-minute changes to airflows within the space in response to performance. This is a very complex process requiring hardware and software that goes beyond the traditional HVAC installations,” he says. In the “risk-averse world” Merrill describes, the caution is understandable, but he thinks the potential is there.


Cambridge Pharma

By adjusting cleanroom airflow based on environmental factors, the room solely receives the volume of air required to maintain critical parameters within compliant levels – namely particle concentration, microbial contamination, temperature, humidity and differential pressure. In case of a contamination event, the system is able to rapidly increase airflow to offset this rise in contamination and continuously guarantee a compliant environment for operation.

This approach ensures a compliant cleanroom environment at all times, which is especially valuable during high-emission processes such as room cleaning or the operation of equipment. Interestingly, when compared to a static cleanroom, a dynamic space is able to deal with contamination in a more effective manner, seeing a significantly shorter recovery time than that of a cleanroom utilizing a fixed air change rate.

The approach to qualification follows a similar method to that of a typical cleanroom using a fixed air change rate. This involves qualifying the space at a selected low supply air rate, which for Cambridge Pharma’s sterile fill finish (EU GMP Grade C) cleanroom is 5 air changes per hour in the “at rest” condition. During performance qualification (PQ) the cleanroom is closely monitored under various ‘worst-case’ scenarios and other potential operating conditions to assure the quality of the environment.

How is room differential pressure affected by dynamic airflow in a cleanroom?

Controlling the supply and return or extract air flow rate of a cleanroom space is essential to maintaining room differential pressure. When air is introduced at an increased rate (as a response to increased particle concentration), the variable air volume (VAV) system will adapt to remove a similar quantity of air from the space, thus preserving the existing differential pressure regime. The use of VAVs allows for highly precise attenuation of airflow and thus is a key enabling technology within a dynamic cleanroom control system such as ICCS®. Other technologies, such as interlocking systems that only allow for the opening of a single door at a time, are also crucial to ensuring correct room pressurization.

Where does dynamic cleanroom control sit within a contamination control strategy as outlined in Annex 1?

Annex 1 develops the concept of a Contamination Control Strategy (CCS) further than any prior GMP documentation. In this regard, Annex 1 specifically references the use of monitoring systems within cleanrooms to “optimize the detection of environmental contamination”, sections 2.3 & 2.5. As the ICCS® continuously monitors critical parameters (such as contamination) to understand the amount of airflow required to maintain a quality environment, it can be said that this technology is closely aligned with the concept of a Contamination Control Strategy as established in Annex 1.

Current GMP regulation such as Annex 1 further supports the deployment of dynamic cleanroom control technology. As stated in section 2.1 “The use of appropriate technology should be considered to increase the protection of the product… and assist in the rapid detection of potential contaminants”. By employing ICCS® in a cleanroom facility, it is possible to quickly manage and abate contamination levels thanks to the use of real-time data informing the system.

How much energy can a dynamic cleanroom control system save?

In our experience at over 300 life science sites around the globe, the Cambridge Pharma facility represents one of the most energy-efficient cleanroom spaces in the world. Consuming just over 200kWh per meter squared a year, the new facility has benefited from a combination of energy-efficient design alongside dynamic demand-based airflow provided by ICCS®. Ultimately, this has resulted in an 80% reduction in energy consumption when compared with a typical life science cleanroom space.


Air Flow Control and Continuous Particle Counters

With rising energy prices, many cGMP and non-cGMP pharmaceutical companies are looking into continuous particle monitoring as a good option even when not demanded by regulation. ABN Cleanroom Technology's Jo Nelissen explains.

As a result of rising energy prices, we notice that many cGMP and non-cGMP companies are considering installing a continuous particle counter in their cleanroom. Since continuous particle counting within cGMP is only a requirement in Grade B and Grade A environments, it didn’t happen often in other cleanroom environments until today. Companies are finding that the investment cost of an online particle counting system pays for itself very quickly and opt for this interesting investment. A shift in the cleanroom world that is fully in line with our patented VIX concept and which we therefore completely approve.

Air Change Rate takes a big bite out of energy consumption.

The predetermined Air Change Rates (ACR) needed to achieve a certain classification are usually drawn up from rules of thumb and assumptions.

As can be seen in the table below, it has been established that the air in an ISO Class 6 environment must be purged no less than 50 times per hour. From our expertise, we find that these values have been built in with far too much certainty.

A major flaw, for example, is that it does not consider variable factors per specific cleanroom, such as the number of operators and their clothing protocols, the contamination of machines, or the processes taking place in the cleanroom. This often creates an overkill in terms of air changes, which will result in unnecessarily high energy consumption.

By integrating a continuous particle counter, real-time integer data on contamination inside the cleanroom can be extracted. Based on this data, it can be determined how many air changes are needed to achieve certain cleanliness classifications.

Energy savings is currently a hot topic at every company operating a cleanroom, no doubt for that. As a result of our patented VIX concept, we can configure our cleanrooms in various ways, allowing savings to be made in different manners:

Saving 1

As already indicated, we see that the particle level in many of our cleanrooms is often "too good" for the requirements of the critical environment. In other words, the ISO rating that is achieved is too high. The VIX concept allows us to lower the Air Change Rate at any time. This makes it possible, for example, to set a day regime (e.g.: 35 ACR) and night regime (e.g.: 15 ACR). Based on this information, we can decide if we go one step further in lowering the ACR. The main advantage about VIX is that the actions above have no impact on the pressure cascade that was envisaged in advance. The entire VIX system operates without any pressure as a result of energy-efficient EC fans on the extraction side that operate stepless without pre-pressure. This is in contrast to VAV-valves that always require pre-pressure and cannot be controlled steplessly. Not to mention the disruptive flow noise of a VAV-valve and the time delay between control and action.

Saving 2

Maintaining the relative humidity inside the cleanroom takes a big bite out of its energy consumption as well. Whereas humidification is required in winter, more dry air will need to be blown through the cleanroom in summer. The VIX concept allows us to switch off the RH when there is no production, so no humidity control is active. Moreover, we can always shift the RH limits within production time based on the actual status in the cleanroom.