Optimizing Airflow To Keep Clean Room Environments Sterile

Clean rooms are controlled environments that filter out airborne pollutants and bacteria. The global clean room technology market, particularly in pharmaceutical and biotechnology, is expected to grow to more than $12B by 2029, up from nearly $9B in 2024. 

While clean room concerns, including access to sustainable power and keeping up with construction demand, are being addressed, one key challenge remains: maintaining optimal airflow to keep these environments sterile.  

Phoenix Controls, a leading manufacturer of precision airflow and pressure control systems, discovered years ago that while the International Organization for Standards, or ISO 14644-4:2022, had a guide of prescribed air change rates, or ACR, in previous editions for clean rooms, it was difficult to find information like emission data to calculate them yourself.

The ACR table was designed to assist engineers in sizing the mechanical system for the desired ISO class. With this alternative to calculation, engineers could size mechanical systems more easily, but it made the sizing and air exchange more conservative to cover many unknowns and potential differences in facilities. 

David Rausch, Phoenix Controls business development manager for its healthcare, research and cleantech markets, said that since ISO standards have updated protocol from a prescribed air change rate approach to a more effective air exchange performance-based approach, this has allowed designers and clean room owners and operators to meet cleanliness standards while meeting their mission of sustainability goals in reducing greenhouse gas emissions.

“That gives the designers the ability to use the technology out there to reduce the amount of air exchange to meet the cleanliness requirement or the sterile requirement,” he said. “Our venturi valve technology allows you to more effectively manage and control the air exchange in the space at a lower air exchange than what is currently being designed today.”

Rausch said that meeting the new requirements all starts with the right clean room design. When operators need to rethink airflow strategies, education and awareness are key.

“You can do more with less air,” he added.

Operators and engineers are becoming more knowledgeable, thanks in part to the American Society of Heating, Refrigerating and Air-Conditioning Engineers, or  ASHRAE Technical Committee 9.11, which oversees the scope of HVAC air conditioning systems for clean rooms and clean spaces. This design guidance considers and incorporates the clean room process, product and facility air conditioning related to the process ventilation for research and development, manufacturing, assembly and testing.

TC 9.11 has representation from many industry stakeholders. Insights from the owner, design engineer and the product equipment manufacturer all ensure a comprehensive design solution that meets the demand and needs of the cleantech industry. Many representatives are liaisons to other standards, like ISO, to further ensure a cohesive approach. Those ASHRAE clean room design guides and handbooks are being updated and are due out in 2026. This protocol is something that Phoenix Controls follows closely. 

“We’re fortunate to offer a technology that fits within those design guidelines and performance-based strategies for engineers,” Rausch said. “ASHRAE TC 9.11 gives great guidance to see where these strategies can be implemented safely and with little risk, reducing operating costs and energy consumption.”

While implementing changes in a clean room environment can be challenging, the company’s venturi valve technology has different levels of intelligent controls that can be implemented and adapted over time, depending on a facility’s needs, usage and more. 

On one level, the venturi valves provide performance-based ventilation by using a mechanically pressure-independent design with a spring-loaded movable cone assembly that automatically adjusts to pressure changes in the duct to maintain precise airflow without needing external sensors or calibration in the field.

Venturi valves are more effective than a traditional air variable control damper, or terminal box, when controlling airflow to maintain directional flow. They have a faster response time and better accuracy and don’t depend on electronic sensors that measure changing pressure in the duct to manage airflow.

“If an operator isn't ready to change the air volume due to scheduling or performance requirements in the space, they can keep it at a constant volume,” he said. “But because the pressure control is more precise and stable, an operator can reduce the air exchange up to 30% more than a variable air damper.” 

The second level involves implementing more control intelligence in the operation of the venturi valve in the HVAC systems. Rausch said operators can start to introduce “two-state” control — airflow scheduling for unoccupied times versus occupied times — without compromising pressure control in the clean space. The venturi valves all work together, tracking each other and maintaining an offset to keep the directional flow in place. They can reduce the air exchange during unoccupied times and schedule more air exchange when the space is in use. 

The third level of control is demand-based ventilation. This requires an environmental control monitoring system that takes data from environmental sensors to vary the air exchange up or down depending on the cleanliness of the space. The monitoring systems can be designed with continuous monitoring capabilities or scheduled, Rausch said.

“Since you have the data from an environmental control monitoring system, the facility can see how dirty the space is based on process or activity and adjust the air exchange without compromising pressure stability,” he said. “You can’t really do that effectively with a variable control damper because it's too unstable. With a venturi valve, if the sensors are showing low levels of contamination, the air exchange can be lowered, so instead of 30 air changes per hour, the operator can manually reduce this to, say, 22 air exchanges per hour.”

He added that a 25% reduction in airflow saves 58% in energy. High particulate generation time frames are typically only several hours a day, resulting in opportunities to save energy by variable airflow to maintain cleanliness class. This process can be done manually by the operator after reviewing the data, or it can be done using automated controls.

“Once you have this base mechanically pressure-independent venturi valve infrastructure in, the facility can adapt and start to evolve the performance of the HVAC system over time,” Rausch said. 

These control levels give clean rooms more flexibility and can help reduce energy consumption, lower greenhouse gases and lower operational costs without compromising the cleanliness of the space, Rausch added.

This idea of implementing venturi valves is becoming more widespread. Rausch spoke on a panel at the Reliability Ireland conference in September, focusing on pharmaceutical manufacturing and the need for reliability in operations and equipment.

He said that from an HVAC standpoint, the conversation was around stability and maintaining reliable pressure control. Without these key components, downtime in clean rooms will increase, leading to reduced efficiency and even poor product quality conformance. The venturi valve is an answer to this performance need. 

“The use of the venturi valve eliminates all that, maintaining stable pressure while still varying the airflow to save operational costs and energy consumption,” he said. “At Reliability Ireland, this was introduced as a new approach that can now be enabled, given the ISO standards changes in 2022.” 

Rausch predicted that clean rooms will become more versatile spaces that can be repurposed and evolve with growing demands across a variety of industries. He said he is confident that Phoenix Controls’ venturi valve will continue to help pave a pathway for more sterile and energy-efficient clean room environments.

“Clean rooms are growing in numbers, and the energy demand is a real concern for the expected growth,” he said. “We’re providing ways of managing the HVAC energy demand more efficiently without compromising safety and contamination requirements.”

This article was produced in collaboration between Phoenix Controls and Studio B. Bisnow news staff was not involved in the production of this content.

Studio B is Bisnow’s in-house content and design studio. To learn more about how Studio B can help your team, reach out to studio@bisnow.com.