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Indoor air contains many different compounds , some of which have a negative impact on health or comfort :
• Gases : for instance , formaldehyde , organic chemicals and inorganic chemicals
• Particles : for example , dust and combustion products
• Radioactive gas : such as radon
• Biological : for example , mould , fungi , pollen and dust mites
• Water vapour : or humidity
Most of the pollutants come from sources indoors , from :
• Human beings and their activities : particles from cooking , products for cleaning and personal care , consumer electronics and electrical office equipment
• Building materials : thermal insulation , plywood , paint , furniture and floor / wall coverings
From outdoor sources , there is pollen , traffic and industry . Radon exists naturally in the ground and enters the building through the floor construction . It is important to use the principle of source control to minimise the concentration of pollutants in the indoor air
To better understand the impact of indoor air on our health , we need to consider the amount of air we breathe per day . An average person consumes 2kg of food and water a day , but breathes in 15kg of air a day ( 12 000 litres ). The health impact is clearly important .
On average 90 % of our time is spent indoors , so most of the air we breathe comes from indoor environments .
The individual or combined effects of the many compounds in indoor air on human health are not fully understood , but major research studies have shown that indoor air quality has an important impact on the health of humans in buildings .
SICK BUILDING SYNDROME The term Sick Building Syndrome ( SBS ) is used to describe situations in which building occupants experience acute health and comfort effects that appear to be linked to time spent in a building , but for which no specific illness or cause can be identified . The complaints may be localised to a particular room or zone or be widespread throughout the building . As can be seen from the chart below , ventilation has the highest impact .
The symptoms of these problems include headaches , eye , nose or throat irritation , dry cough , itchy skin , fatigue and concentration difficulties . These symptoms are defined as SBS symptoms , and the World Health Organisation ( WHO ) concludes they are found in 15-50 % of all buildings . A review showed that air-conditioned office buildings have a 30-200 % higher prevalence of SBS than naturally ventilated buildings . The symptoms are believed to be caused by poor indoor environments and can be helped by improving the air quality .
Living or working in damp buildings are among the indoor air quality factors that are most likely to cause illnesses . Investigations into thousands of buildings have shown that damp buildings can cause illnesses such as coughs , wheezing , allergies and asthma . A damp building is a building with an increased humidity level ( the exact risk level of humidity is not known ).
Investigations on the mental performance of occupants in office buildings and schools have shown that poor air quality reduces mental performance , while good air quality improves performance .
Deon , there are several ways to bring fresh air into our homes . Ventilation systems can be natural , mechanical or hybrid ( a combination of the two ). There are two ways to ventilate or cool buildings , namely ; actively or passively .
• Active ventilation or cooling – this refers to systems where mechanical components or other energy-consuming components such as air-conditioning systems or fans are used .
• Passive ventilation or cooling - this is a technology or design feature used to ventilate and or cool buildings with no energy consumption such as natural ventilation by open windows . Passive cooling is a measure that consumes no energy to cool buildings . It includes concepts such as : solar shading , thermal mass , ventilative cooling .
NATURAL VENTILATION Natural ventilation uses natural forces to exchange the air in a building . The driving forces are wind and temperature differences . Natural ventilation refers to the amount of air that enters a building uncontrolled without the aid of a mechanical device , such as a fan . The force that provides the pressure difference causing the air to flow may be the result of wind action or a temperature difference between the inside and the outside of the building , called stack effect . Stack effect is the pressure difference caused by the variation in temperature and humidity - and therefore density - between the air inside and outside the building . In buildings over the height of 30m , these pressure differences cause summer and winter infiltration and exfiltration , as follows :
• Summer : Infiltration at the top of the building and exfiltration at the bottom
• Winter : Infiltration at the bottom of the building and exfiltration at the top
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Sick Building Syndrome : primary causes
RACA Journal I March 2025
These opposite directions of air flow through the building balance at a point somewhere near the centre of the building .
In South Africa , where winters are mild , the stack effect is
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