HVAC SYSTEMS
documented that 2220 GP surgeries and 248 hospitals in the UK are in locations with air pollution above World Health Organization Standards. Poor air quality has been the catalyst for greater discussion about the needs for adequate ventilation – natural or otherwise – and the Government, NHS, and other associated regulatory bodies, have rapidly got on board with this.
reducing pollution, with one of the key focuses being on ventilation and air quality monitoring. The framework considers the need for improvements to the efficiencies of ventilation systems, and considers the volume of fresh air against recirculated air, based on both the clinical environment (i.e. operating theatre versus reception area), and the pollution recorded in the geographical area. Also in 2018, another report, published by the British Lung Foundation, and entitled Toxic Air at the Door of the NHS,4
COVID-19
Good ventilation has been very well publicised as a method of reducing the opportunities for airborne transmission of COVID-19, and, as a result, we at Barkell are seeing a surge in the demand for advice, maintenance visits, service checks, refurbishments, and replacement of air- handling units across the board – in locations ranging from office buildings to warehouses, and from hospitals to pharmaceutical laboratories.
As the UK has grappled to maintain the balance between staying open and staying COVID-safe, effective ventilation has played a major role in the strategies of many businesses and organisations to create confidence as employees return to work. Hospitals and other clinical settings often have the most physically vulnerable people in a concentrated area, where the risk of airborne virus is possibly higher than average, and have had to adapt existing facilities accordingly.
Air-handling units and ventilation in healthcare Air handling units are the lungs of the healthcare building – providing fresh, clean, conditioned air to occupied spaces, and removing and exhausting the contaminated air within. Ventilation is crucial to the healthcare environment for several reasons. On a surface level, it provides a safe and comfortable environment for patients and staff by bringing in fresh air and controlling the air temperature, humidity, and odours through the building. Beyond that, it is also crucial in reducing airborne infection risks in critical areas of the building, where its purpose is
38 Health Estate Journal September 2021
order to make meaningful decisions as to how they might apply to a specific project. Those already familiar with HTM documents will recognise that there is no ‘one-size-fits- all’ approach to their
It is essential that healthcare AHU systems are designed and built to offer resilience in the event of component or system failure, and that they are easily accessible for maintenance.
to reduce bioburden, via filtration and dilution of the air. It also contributes to maintaining spaces at appropriate pressure to prevent the ingress or egress of dangerous microorganisms. Mechanical ventilation is also critical in other healthcare-associated facilities, and may be deployed to ensure quality assurance compliance in pharmacies and sterile services departments, or to protect staff from harmful and toxic substances in laboratories.
The failure of air-handling units in hospitals can have catastrophic consequences, since, given the specialised nature of the services provided within such facilities, it is very difficult to readily provide equivalent service elsewhere. This can lead to reduced clinical capacity, and, in the worst-case scenario, interruption to services and potential loss of life as. It is thus essential that these AHU systems are built to offer resilience in the event of component or system failure, and that they are easily accessible for maintenance to facilitate resolving any issues, and getting the system back to full operational status swiftly.
Using efficient and sustainable technologies Air-handling units also represent a significant portion of the total energy consumption in healthcare buildings, and the design of ventilation systems should therefore take this into consideration by utilising, where possible, the best available, most energy-efficient, and sustainable, technologies. These, aided by intelligent building management and local controls systems which accurately maintain the conditions in the space, along with a high- quality installation, commissioning, and maintenance plan, will provide the maximum health benefits for the minimum energy input.
HTM 03-01 (2021) AHU mechanical design requirements
While it is possible to summarise the bulk of the revisions in a few paragraphs, it is important to either fully understand them, or to consult with a supplier who does, in
implementation, and while this is a positive thing – because it allows for environmental and economic factors specific to each project to be taken into consideration – it also leaves a lot of ‘grey areas’, which are left open to interpretation and discussion. I will, however, do my best to briefly address the
main areas of change.
New standards and legislation Since the publication of the 2007 version of HTM 03-01, much has changed on the scope of legislation and standards for air- handling units across the industry. The EcoDesign Directive for ventilation products (EU 1253/2014) came to force in 2016, compelling AHU manufacturers toward more energy-efficient technologies and transparency in their technical documentation. In 2018, filtration standards were updated, with BS EN 779 being replaced with the new global filtration standard, ISO 16890, which brought the classification of particulate air filters closer to their real-world applications and the WHO indoor air quality guidelines. In 2019 standard BS EN 1822 regarding the testing and classification of HEPA filters, and BS EN 13053 on the rating and performance of air-handling units, were both updated. The COVID pandemic in 2020 has brought increased concerns about ventilation, and a general increase in the number of recommended air changes per hour in common, public spaces. All these changes, among many others that took place in prior years, needed to be accommodated in the revised Health Technical Memorandum.
Quality casing construction A major area of concern is on the selection of appropriate build materials to prevent corrosion and the growth of microorganisms inside the air-handling unit. The use of corrosion-prone and degradable materials in air-handling units can lead to a quick deterioration of the plant, accumulation of dirt and organic material inside, and the associated growth of microorganisms such as moulds and bacteria. These can be very threatening in a healthcare setting, especially for immunocompromised patients, such as those suffering from cancer or leukaemia, since moulds, for example, can be especially dangerous to these vulnerable patients.5,6
The new guidance requires that
long lasting, non-corrodible, non- degradable materials are used in the manufacture of the air-handler casing. The
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