BSEE-MAR22-PG32NEW.qxp_Layout 1 22/02/2022 11:25 Page 32
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MAINTENANCE & REFURBISHMENT The role of maintenance in ensuring good IAQ
Martin Passingham, product manager at Daikin, explains why correctly maintaining and cleaning a building’s ventilation can be just as key as its initial design and installation
systems have never been so important. As the environmental impact of the built environment is now a key focus, buildings are increasingly being designed with high levels of air tightness to optimise energy usage. However, this means that IAQ can be impacted if ventilation is not designed correctly or operate as intended.
W The importance of good IAQ
Air pollution has long been seen as a major health issue. In addition to the long- and short-term effects of exposure to pollutants, there is also growing evidence that poor air quality may impact physical and mental health, concentration and productivity. With people spending an estimated 90% of their time indoors, the quality of the air is essential.
Indoor air quality is influenced by a wide range of factors and there are many sources of air pollution, from both inside and outside the building. Within the building, this includes dust, damp and mould, volatile organic compounds (VOCs) emitted by wall and floor coverings, furniture and appliances, and emissions from office equipment and industrial machinery. The building occupants themselves also affect IAQ by exhaling carbon dioxide (CO2) and spreading germs and viruses. External sources such as road vehicles, industrial processes, waste incineration and construction activities all generate air pollutants, including particulate matter, nitrogen dioxide (NO2) and carbon monoxide (CO). These substances, along with allergens such as pollen, can be brought into a building through natural or mechanical ventilation and via infiltration through the building fabric.
Cleaning and maintenance best practice
Ventilation clearly has a key role to play in achieving high levels of IAQ. As part of a building’s wider HVAC and climate control system, effective ventilation can help to extract water vapour, odours and airborne pollutants, including colds and viruses.
One of the most important elements in maintaining IAQ and high levels of efficiency are the units’ filters. It is firstly important to check the correct type of filter is fitted based on the pollutants present in the internal and external environment and the level of air quality that needs to the achieved. The system must ensure
32 BUILDING SERVICES & ENVIRONMENTAL ENGINEER MARCH 2022
that particulate matter (PM) in the air is kept under the PM threshold limits set by the Air Quality Guidelines published by the World Health Organization (WHO). The recommended limits are: an annual mean for PM2.5 of less than 10
micrograms per cubic metre (µg/m3) and an annual mean for PM10 of less than 20 µg/m3. In addition to this, the type of building will
dictate what level of filter is required. General filters that capture larger, heavier particles, such as dust, will be suitable for lower risk, lower pollutant environments. In contrast, fine filters that can capture particles the size of bacteria may be needed for applications such as healthcare buildings, while high-efficiency particulate air (HEPA) filters or ultra-low particulate air filters (ULPA) filters may be required for specialist environments, such as clean rooms and ultra- clean operating theatres.
These filters must also be cleaned regularly to keep the system operating efficiently and ensure good IAQ. A clogged filter will force the unit to work harder to draw air through the less porous structure and can reduce airflow across the coil, leading to the system using more energy to deliver the required performance. This not only wastes energy but can shorten the life of the system. A blocked filter also increases the chance that contaminants can inadvertently be blown into the room, impacting the air quality of the environment. Additionally, a unit working harder will produce more internal condensate and, if the drip tray is not draining correctly, the condensate can build up and overflow, causing damage to the fabric of the building.
The level of cleaning and maintenance that is required will depend on factors such as the type of building, how it is used and the characteristics of the indoor environment. For busy environments with a large number of people or dust generating activities, the filters may have to be cleaned as
regularly as once a month. While this is a relatively simple process of removing and cleaning the filter to remove the dust and contaminants, or replacing, this can be time consuming for larger buildings or businesses with multiple sites. One solution to this is to invest in indoor units with auto-cleaning capabilities or fit auto-cleaning duct accessories to the back of ducted units. Both types prevent dust accumulating on the unit’s filter by capturing and containing dirt and debris in a dust box. This can then be emptied quickly and easily with a standard vacuum cleaner, minimising maintenance requirements. Also, some self-cleaning units will include the ability to position the suction port a short distance away, making it as convenient as possible to empty. The simplicity of this process means that it can be incorporated into the building’s general cleaning practices. In addition, in some environments there is a greater risk of contamination occurring in the condensate trays. For example, in areas where there are higher levels of moisture and a large number of people, such as night clubs and leisure facilities, bacteria can accumulate in the tray. For these buildings, inspection and cleaning of the condensate trays should be carried out on a regular basis depending on the requirement. Finally, the system intakes and exhausts as well as the outdoor units should be inspected regularly for signs of dirt, debris, contamination or damage from weather and animals. This can be easily overlooked as the focus of cleaning and maintenance can be focused on the indoor units. Ventilation is essential for good IAQ, but a cleaning and maintenance schedule appropriate for the type of building must be established and followed to ensure the system functions effectively and efficiently. The introduction of technologies to make this process simpler will allow it to be incorporated more easily into the general maintenance of the building.
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ith increasing attention being paid to indoor air quality (IAQ) and ensuring people are provided with a well-ventilated, healthy and clean interior space, HVAC
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