Apple-Catechin – The hidden fruit in Air Conditioning
Phil Deverick, Commercial Manager, Fujitsu General Air Conditioning UK talks about the increased interest for greater indoor air quality
The interest in indoor air quality not only exists within the building services sector, it is widespread - at government level and also with growing prominence in the general public. Media and scientific factors play a part in creating an endless circle of publicity, with research highlighting the cause and effects of the air we breathe, emphasising not only achievements, but more importantly shortcomings, tragedy, shock and awe.
Is all this interest warranted? The answer is yes, as this is currently one of the most important environmental issues we are experiencing, alongside climate change. In September 2020, Professor Jonathan Grigg described the published findings of some ground breaking research conducted at Queen Mary University, London. He said: “Our study for the first time shows inhaled carbon particulate matter in air pollution travels in the blood stream and is taken up by important cells in the placenta”. The research indicates the importance of indoor air quality by illustrating that the air we breathe is even shown to have a direct effect on our unborn children.
Variation of air pollution
Air pollution exists in many forms. Volatile organic compounds such as carbon dioxide, carbon monoxide, ozone and formaldehyde. Biological components such as bacteria, fungi, pollen and odours. And Particulate matter, such as black carbon, which is caused by the incomplete burning of items. They are all defined using a scale of diameter in microns. This large variation is the reason why the issue of indoor air quality requires focus from all areas of society to improve air quality.
The World Health Organisation defines good health as ‘a state of complete physical, mental and social well-being, not merely the absence of disease and infirmity’. This definition, whilst subjective, indicates that there are many different factors to achieving good health.
Most system design guidance in the past associated with ventilation has focused on ventilation rates, overlooking the actual air quality that is being maintained in the spaces we occupy. This is not necessarily due to naivety, but in fact demonstrative of the lack of tools available to monitor and control the large ranging variety of components attributed with air quality.
Sick building syndrome
Since the identification of the relationship between a person’s ill health and the building they occupy by the WHO in 1984, research has developed a firmer understanding, attributing shortfalls of the heating, ventilation, and air conditioning services within a building as the main attributes responsible for the cause of ‘Sick Building Syndrome’. It has been more recently and publicly acknowledged as one of the vectors behind the spread of the virus SARS.
The ventilation effectiveness on pollutants, set by the manner and rate in which air is moved through a space, is now considered at the design stage of any associated building or ventilation system. Part F of the building regulations ensures acceptable levels of indoor air quality depending on the application of the occupied space. The assessment on whether the design is based around air flow rate or the number of air changes within a space per hour is determined by type of contaminant that is being focused upon and the rate of its occurrence. If the contamination is via a short burst, then the number of air changes per hour is important to dilute the concentration, but if the pollutant source is within the room or being introduced from outside, then the ventilation rate is important to maintain a steady acceptable concentration level.
Contaminants do not always occur from external sources as we might think. Metabolic CO2 is produced as we breathe - the by-product of our respiratory system and dangerous if we are exposed to high concentrations. The rise in CO2 concentration in the outdoor air, along with the maximum exposure levels are listed in Part F of the building regulations as a control medium for indoor air quality and more likely to be removed by extract rather than direct filtration.
We assume air filtration is always active within the air handling unit or other mechanical device that is being used to introduce fresh air into a building; sometimes forgetting that the devices placed within a space, conditioning the air to achieve thermal comfort are also effective means.
Concentration of contaminants
The amount of particulate filtration varies depending on the type of application, the contaminant type and concentration being introduced from outside, as well as the level of indoor air quality required. Course disposable or washable pre filtration is used to remove particle sizes above PM10 (particulate above 10 microns in diameter). These are generally less expensive and help to maintain the life expectancy of intermediate or high efficiency filters, as well as the mechanical plant introducing the air.
Air conditioning filtration generally starts with an intermediate filter level of PM2.5. and protects the heat exchanger operation by removing contaminates from the air, such as dust, and liquid droplets. As they condition air by recirculation, they effectively become additions in the design for good indoor air quality, but are rarely taken into consideration within the air treatment design.
Methods such as electrostatic and ION filtration are used to improve effectiveness by attracting particles to the mesh in a filter rather than solely relying filtration mesh size to trap contaminates. If we are to trap biological contaminates within a filter, should they just be left to accumulate on a surface and continue to be a hazard?
A lot of research has taken place to stop the continued growth of bacterial contaminants within a filter. The Apple-Catechin filter, contained within Fujitsu air conditioning fan coils, removes mould spores and harmful microorganisms by using electrostatic filtration. Absorbed onto the filter because of the static electricity, further growth is inhibited by the use of an organic compound, polyphenol. Whilst polyphenols are found in plants, fruits and vegetables they do not have an active role in growth, but are important to the defence mechanisms against viruses, bacteria and fungi. They interact with bacterial cell wall components and membrane, inhibiting bacterial growth and functionality. This deactivation prevents concentration levels rising to harmful levels if the filter is disturbed and provides an element of control to biological contaminates which can be otherwise missed.
As always within the building services sector, cost plays an important role in the selection and application of products used to provide our heating, ventilation and air conditioning services. Unfortunately, the greater the number of control strategies required to monitor indoor air quality involves greater associated design costs and capital expenditure. The greater the level of air filtration, inevitably results in higher operating costs of the air movement equipment because of the higher-pressure resistances it has to overcome. Building efficiency drives design, highlighting wider environmental concerns and significant operational costs as the priority. Research has been carried out for a number of years highlighting the cost of the lack of productivity and staff illness associated with the buildings we occupy, but how often is this taken into account in order to exceed design regulations for indoor air quality? Should we just continue to develop strategies in the smaller products, like air conditioning fan coils so they are applied as standard? What price can anyone put on a person’s long-term health?