SPECIALIST FACILITY DESIGN
cleaning. There are a number of materials that are already tried and tested for use in environments classified as ‘clean’, but an aseptic facility specialist will also be able to advise on any new materials and antimicrobial technology. It is important to avoid assumptions about standard specification of floor, wall, ceiling, and coving materials, as this can sometimes result in value engineering opportunities being overlooked.
Ease of cleaning should also be supported by the design of surfaces and the interface between walls, floors, and ceilings, along with any doors and windows. The design should avoid awkward details and ledges where dirt or bacteria could collect. Sharp corners, joints, crevices, and horizontal surfaces, should also be avoided, where possible. Minimising the build-up of bacteria through careful design is only one of many architectural design considerations; equally important is the need to maintain pressure regimes. Air loss can occur through light fittings or plug sockets if the back boxes have not been specified and detailed to maintain air pressure regimes. Potentially, this could compromise compliance to the relevant cleanliness grade. Consequently, all elements of the specification should provide a high level of airtightness, while still being accessible for maintenance.
Interlock door systems
Pressure regimes in airlocks are usually supported through the use of interlock door systems, which only allow one door to be opened at a time. In principle, it may be assumed that the use of PIR sensors to control the door interlocking provides the cleanest option, because the operators are not required to interact with fittings. In reality, however, this can lead to nuisance locking / unlocking of doors, resulting in a restriction of access to the area for other users. A more practical approach is
assess the air cleanliness of the facility as part of our design process. This, in turn, can help to refine both the architectural and building services design elements of the project.
A sterile environment that safeguards the purity and accuracy of the formulation is needed for aseptically prepared drugs.
‘touchless’ or close proximity sensors, or the use of a conventional push button. Both of these systems operate only when users physically request access via the interlock system, which checks the open/closed status of all other doors, and grants access when available. As operatives are either dressed in correct garments for the grade of cleanroom and its cleaning regime, or are entering a change room and will be donning additional garments, the use of push buttons does not have a negative impact on the cleanroom environment.
Ventilation and pressure regimes One of the key specialist areas of an aseptic facility is the design of high performance ventilation systems, as these play a vital role in reducing airborne particulates within the facility, and eliminating the risk of cross-
contamination. The particle count for the air within a cleanroom is dependent on the volume and quality of the supply air, management of contamination sources, and expert design of the ventilation system. We use mathematical algorithms and software to model airflows and
Design of the ventilation system is one of the key areas where specialist expertise must be applied to the facility’s specific physical, workflow, and operational conditions. Air change rates are traditionally specified using proven and historical air change frequency, aligned to the required cleanroom classification. However, the use of standard data alone can result in energy-hungry ventilation systems that require large amounts of fresh air. NHS Trusts are mindful of the need to build energy-efficient and operationally cost-effective assets, and working with a specialist in engineering aseptic facilities ensures that the operational needs of the hospital are met in the most energy-efficient way possible. Such expertise can contribute to reduced build costs, improved spatial efficiency, lower running costs, and a better carbon footprint.
Calculating air change rates At BES, we use a number of tools to help calculate required air change rates, designing the mechanical services to meet the bespoke requirements of each aseptic facility. These include mathematical calculation of ‘clean up rates’, such as the WEI Sun calculation method, for example, which uses particle balance equations to mathematically model a particular cleanroom. We use input data that includes the level of room cleanliness required, the number of people who will occupy the facility, the particle emissions from cleanroom gowns, and the outdoor environment particle concentration at the specific location. This ensures that the design is based on both operational factors and the facility’s physical location. Computational fluid dynamic (CFD) calculations are also now commonly used, enabling us to model the room in full 3D, including all finishes and equipment, heat gains, and heat losses. We can then apply ventilation rates to the model, creating an accurate graphical representation of the dynamic room state, and thus helping to inform the final design solution.
Validation
Validation is an extensive qualitative and quantitative process that should involve both the construction team and the hospital.
Validation is a critical stage in delivering an aseptic facility. Described by the US Food & Drugs Administration (FDA) as a process to ‘establish documented evidence which provides a high degree of assurance that a specific process will constantly produce a product meeting its predetermined specifications and quality attributes’, it ensures that the facility is operating in line with its agreed design intent.
January 2020 Health Estate Journal 73
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