AIR-HANDLING SYSTEMS Air pollution’s impact
As we emerge from the current crisis, this reassessment will help to reinforce the message that AHUs will continue to play a vital long-term role in the ongoing threat posed to human health by air pollution, which is responsible for as many as 36,000 deaths a year in the UK, according to PHE. Long-term exposure to airborne contaminants increases the risk and severity of asthma, and is also linked to coronary heart disease, stroke, respiratory problems, and lung cancer. It costs our economy upwards of £20 billion a year, largely due to the additional burden on the NHS.
Rethinking ventilation strategies Growing awareness of the impact of poor indoor air quality (IAQ) on health and productivity had already forced many building owners and managers to rethink their ventilation strategies before the coronavirus pandemic. Emerging from the crisis will hopefully ensure that there is even more concentration on this issue. AHUs will, therefore, be under increased scrutiny, because of their role as interfaces between potentially highly polluted outside air and the indoor environment. Modern AHUs are also relatively complex systems, containing a series of active components like fans, heating and cooling coils, and air filters, as well as sound attenuation technology and humidification. They are subject to the updated European Ecodesign Directive – specifically ErP 1253, which was first adopted in 2014, and came into force two years later to ensure that systems meet exacting energy efficiency standards, but without loss of performance. As a result, most AHUs now incorporate heat recovery in order
Daikin Applied said: “Modern AHUs are relatively complex systems, containing a series of active components like fans, heating and cooling coils, and air filters, as well as sound attenuation technology and humidification.”
to reduce the amount of wasted heat. Switching this feature off should only be a temporary and precautionary measure during the COVID-19 outbreak. AHUs are also subject to ISO, CEN, and BSI technical standards to achieve compliance with World Health Organization (WHO) guidelines for IAQ where people work and have public access to buildings in heavily polluted urban environments.
Particulates are getting smaller The design issue faced by specifiers of AHUs is that harmful particulates are getting smaller, which makes them more
dangerous when inhaled, as they can penetrate further into the human body. New filtration standards are focused on PM1 particulates (the smallest easily measurable), including those from diesel engines, which have been identified as a Group One carcinogen by the WHO, and have also been linked in recent studies to early onset Alzheimer’s disease. This means that very high standards of filtration are needed, which has a profound impact on the design of the unit and the system as a whole. F7 filters are becoming a requirement, in line with the international standard EN779. This combination of heat recovery and higher specification filters means that an AHU will be subjected to higher pressure drops. This has implications for the size of the unit and its fan power, which, in turn, could lead to the use of larger motors, that consume more energy. This flies in the face of current design trends, which have been moving towards smaller units to reduce capital cost and free up valuable lettable space in commercial buildings.
A Daikin Applied Professional AHU with Thermal Wheel with full unit controls. 58 Health Estate Journal October 2020
Systems that are not fit for purpose As a result, in our highly price-sensitive industry, there is growing evidence that some suppliers to the commercial building sector are simply ignoring the new standards in order to be able to quote a lower price to the client. As standards are rarely policed across the building services sector, this less than ethical approach often pays off – at least for the supplier. However, the outcome is that building owners and occupiers are left with systems that are not fit for purpose, are not legally compliant, and
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