Understanding Airflow Visualization Studies in Cleanrooms
In the realm of maintaining sterile environments, airflow visualization studies are indispensable. They aid in comprehending airflow patterns, detecting potential contamination risks, and ensuring adherence to regulatory standards. This blog post delves into the significance of these studies, their principles, methodologies, and their pivotal role in ensuring the cleanliness and sterility of critical environments.
Importance of Smoke Studies
Smoke studies serve as a vital tool in evaluating and optimizing airflow patterns within sterile areas. By releasing harmless smoke particles, technicians can visualize airflow dynamics, identify turbulence, and assess ventilation system effectiveness. These studies are particularly crucial in environments like operating rooms, cleanrooms, and pharmaceutical facilities, where controlling airborne particles is paramount to prevent contamination.
Smoke studies, conducted by technicians and engineers, enable the identification of turbulence, dead zones, and insufficient air circulation within sterile areas. This information facilitates adjustments to the ventilation system, such as repositioning air diffusers or adding air filters, to enhance airflow and minimize contamination risks.
Additionally, smoke studies aid in pinpointing potential sources of contamination, including air leaks and improper door sealing, thus ensuring compliance with standards and reducing the risk of contamination to sensitive processes, products, or patients.
Regulatory Requirements and Industry Guidance
While the new Annex 1 reinforces the importance of Airflow Viz (Clauses 4.15, Qualification, 4.31, EM locations and 7.18, Operator Training ) the FDA guidance on aseptic processing from 2004 has always been very clear on this subject: “ it is crucial that airflow patterns be evaluated for turbulence or eddy currents that can act as a channel or reservoir for air contaminants (e.g., from an adjoining lower classified area). In situ, air pattern analysis should be conducted at the critical area to demonstrate unidirectional airflow and sweeping action over and away from the product under dynamic conditions.
ISO 14644-4:2022 adds further reinforcement and guidance as an international standard. There is also Industry guidance from USP <1116>, ISPE and PDA. CETA has issued specific guidance around the importance of the visible medium source should be as close to neutrally buoyant as possible. *
*CETA Certification Guide for Sterile Compounding Facilities CAG-003-2006 -13 Revised May 2015 and CETA Application Guide CAG-014 Airflow Visualization Study Revised March 2022
Key Principles of Airflow Visualization in Cleanrooms
Maintaining optimal airflow patterns within cleanrooms is essential for ensuring compliance with regulatory standards and minimizing contamination risks. Airflow visualization studies serve as a crucial tool in achieving these objectives by validating the effectiveness of ventilation systems and guiding corrective actions where necessary. Whether dealing with unidirectional or turbulent airflow, these studies are indispensable for establishing effective contamination control measures.
Visualizing airflow patterns within cleanrooms and designated zones is imperative to demonstrate adherence to regulatory requirements. These studies aim to prevent ingress from lower-grade to higher-grade areas and to ensure that air does not flow from less clean areas, such as the floor, over operators or equipment that may introduce contamination. For cleanrooms requiring unidirectional airflow, visualization studies are conducted to ensure compliance. Additionally, when transferring filled, closed products to lower-grade cleanrooms via pass boxes, airflow visualization studies verify that air does not infiltrate from the lower-grade areas to the higher-grade zones. Any identified risks to clean areas prompt corrective actions, such as design improvements, to mitigate contamination risks.
Airflow pattern studies encompass both static and dynamic conditions, including simulations of operator interventions. Video recordings of airflow patterns are retained for documentation purposes and play a vital role in establishing environmental monitoring programs. Areas exhibiting slower airflow or reduced flushing are earmarked for further testing, including recovery, clean-up, microbiological, and total particle counting tests, to monitor contamination levels effectively.
During operations, operators and equipment may introduce airstreams into the cleanroom from material airlocks (MALs) and personnel airlocks (PALs). Adequate "clean-up" time is crucial to ensure a steady state air balance and room pressure, facilitated by outward airflow into lower-pressure cascading rooms. This underscores the importance of interlocks and designing MALs and PALs to accommodate sufficient clean-up time.
In summary, airflow visualization studies, akin to smoke studies, play a pivotal role in assessing and optimizing airflow patterns and contamination risks in sterile environments. By visualizing airflow dynamics, these studies facilitate the optimization of ventilation systems and uphold cleanliness and sterility standards across healthcare, pharmaceutical, and laboratory settings. Thus, the implementation of airflow visualization studies is paramount for maintaining the highest standards of cleanliness and sterility within cleanroom facilities.
Understanding Turbulent Airflow Patterns in Non-Unidirectional Cleanrooms
In non-unidirectional cleanrooms, airflow patterns are intentionally designed to be turbulent. This design ensures effective dilution and mixing of both clean and contaminated airstreams, crucial for maintaining a sterile environment. The Cleanroom Contamination Removal Effectiveness (CCS) revolves around this turbulent airflow concept.
Air enters the cleanroom through terminal HEPA filter diffusers, strategically positioned throughout the ceiling. These diffusers should be spaced individually across the room or grouped together, depending on process workflows and activities. The airflow patterns are designed to ensure maximum dilution, while return air locations are designed to eliminate any "dead" pockets of stagnant air that could potentially collect contaminants and redistribute them when disturbed by personnel or material traffic.
Figure X – Actual Airflow Movements and Patterns are NOT SIMPLE
However, in the real world airflow movements and patterns are constantly changing based on the dynamic nature of activities and processes within the Cleanroom, such as material and personnel traffic movements, work in progress and equipment processes.
Given the dynamic nature of turbulent airflow, with multiple air paths and patterns constantly varying based on activity levels within the cleanroom, maintaining air quality becomes paramount. While the stringent requirements of unidirectional airflow cleanrooms may not apply, it is crucial to ensure thorough air exchange and efficient removal of contaminants. Special attention must be paid to minimize any "dead" pockets or zones where airstreams may move slowly, as these areas pose a risk of contaminant buildup, potentially leading to contamination of critical surfaces or transfer through personnel contact.
Technology and Methodologies
The tracer particle method is commonly employed to make airflow patterns visible. By introducing tracer particles into the air stream, technicians can accurately map airflow patterns against design and operational requirements. To effectively introduce tracer particles into a cleanroom, a diffuser manifold is necessary. This apparatus ensures that the vapor from the particles cools and mixes with air, creating a stable fog at ambient temperature and pressure. By preventing full condensation, it avoids the jetting effect that could falsely indicate unidirectional airflow, particularly in areas with dead spaces and eddy currents. Moreover, this method minimizes excess condensation on surfaces within the cleanroom, as the fog exits the manifold at the same temperature and pressure as the cleanroom environment. It's essential to note that water, CO2, or nitrogen-based fogging systems cannot visualize dead spaces or areas lacking airflow as their tracer particles are not neutrally buoyant.
Neutral buoyancy tracer particles ensure faithful adherence to airflow, crucial for accurate mapping of air patterns.
Summary and Take-Home Message
Understanding and managing turbulent airflow patterns in non-unidirectional cleanrooms is essential for optimizing contamination control and maintaining a sterile environment conducive to critical operations and processes.
The information gathered in airflow visualization studies can be used in risk assessments and refine your CCS (contamination control strategy) so you can optimize airflow movements and patterns in cleanrooms, RABS and Isolators, around operator standing positions, movements and interventions, as well as the selection of environmental monitoring locations, operator training and troubleshooting cleanroom contamination issues.
Here are some important examples of the types of scenarios that could be examined when conducting airflow visualization studies to determine what the airflow movements and patterns are in a Cleanroom or a Cleanzone, and why:
If it is “First Air” that is required then it is important to establish whether the airflow is smooth, free from disturbances (such as small, temporary vortices or eddies) and unimpeded
If it is an area where turbulent flow is expected then it is important to establish whether the airflow movements and patterns have any areas where there are instabilities and variability such as temporary fluctuations or where there are air eddying do they any negative impact on critical process steps.
To demonstrate the difference between static and dynamic states and the direction of airflow movements and patterns away from the critical zone
To demonstrate the impact of operator interventions and other personnel activities
To show the impact of equipment and process during Operations
To demonstrate airflow movements and patterns during set-up of equipment and processes
RABS Airflow Viz Study
Potential contamination risks we want to identify investigate, and then remediate can be the result of:
Heat rising from machinery and disrupting the airflow
Obstructions preventing the supply of air reaching a critical area
Obstructions in equipment or process steps that interfere with” First Air” and change a unidirectional flow into a turbulent flow
Entrainment, where contamination is drawn into a clean airstream or local airflow pattern
Stagnant or turbulent areas acting as conduits or repositories of contaminants
When air flowing from personnel is directed towards the critical zone.
It is important to note that Air Visualization is just another step in the effort to optimize cleanroom operation and is not a definitive pass/fail test, because acceptable or unacceptable conditions are not readily definable.
Conclusion and Future Topics
It is almost impossible to design a Cleanroom with a “Crystal Ball” and get it right first time, considering the myriad of factors involved. While the design may involve sophisticated CAD tools and CFD the design must be tested as part of CQV, when ALL the processes and workflows are in place. The real-world test for product quality and patient safety can only take place under simulated Operational conditions.
Airflow visualization studies are instrumental in ensuring ongoing cleanliness and sterility in critical environments. They facilitate the evidence of compliance with regulatory standards, optimize HVAC and filtration systems, and minimize contamination risks.
In our next post, we will delve into the requirements for a formal Airflow Visualization test protocol and the concepts of Recovery Time and Clean-Up Time as defined in the new Annex 1 guidelines, exploring their practical implications.
By shedding light on airflow visualization studies, we aim to underscore their importance in safeguarding the integrity of sterile environments and ensuring the safety of critical processes and products for the well-being and safety of patients.
Stay tuned for our next installment as we explore these critical concepts further!