Interior design
Indoor Air Quality
Wednesday, 12 August 2009
Posted by Niki Fulton at 09:20 AM in Interior design
I asked air quality expert, Leif Wirtanen, "What does indoor air quality mean and how do paints affect it?"
"The term Indoor Air Quality, IAQ, refers to the environmental characteristics inside buildings that affect human comfort and health. IAQ characteristics include the amount of pollutants (volatile chemical compounds, particles, fibres) in indoor air, its temperature and its humidity. The amount of pollutants on indoor surfaces that may be contacted by people, and indoor lighting and acoustic conditions, are also often considered as aspects of IAQ.
When people are indoors, they are exposed to air pollutants generated from indoor sources and to air pollutants that enter the building from outside. Outdoor air, i.e. air from outside the building, enters buildings both via (controlled) ventilation, but also by leakage (windows, doors, ground slabs etc.). Examples of indoor-generated air pollutants include gases and particles produced by tobacco smoking, particles and gases released by mould and bacteria that grow on damp surfaces, and volatile chemical compounds (gaseous chemicals typically containing carbon, hydrogen, nitrogen, and often also other elements) released from building products, furnishings, and household products. People, pets, and plants are also sources of indoor pollutants. Ozone, radon, and various types of particles, are examples of outdoor air pollutants that may enter buildings. Because people nowadays spend a lot of time indoors (up to 90 % of the day), their exposure to most indoor-generated and also outdoor air pollutants may have effect on their comfort and health.
Aspects of comfort affected by IAQ include thermal comfort and olfactory or sensory comfort. Also a broad range of different health effects may result from indoor pollutant exposure. Some pollutants increase the risk of very serious health effects, such as cancer. Some indoor pollutants can cause infectious disease such as the common cold or influenza. Allergy and asthma symptoms may result from indoor pollutant exposure. Indoor pollutants may also contribute to eye, nose and throat irritation, skin irritation, cough, wheeze, headache, and fatigue symptoms, which are often called sick building syndrome, SBS, symptoms or building related symptoms, BRS.
In the context of IAQ the term volatile organic compound refers to any of hundreds of carbon-containing chemicals that are gases at room temperature. They are generally divided into three categories depending on their boiling point: Very Volatile Organic Compounds (VVOC), Volatile Organic Compounds (VOC), and Semi Volatile Organic Compounds (SVOC). Of these have SVOCs the highest boiling point temperature and also the biggest tendency to adsorb onto surfaces. Inorganic carbon-containing gases, such as carbon dioxide and carbon monoxide, are excluded from this definition.
A large number of organic compounds are released into indoor air. Organic compounds also enter buildings with outdoor air. The main sources of indoor-generated organic compounds include building materials, furnishings, cleaning products, office equipment, personal care products, air fresheners, pesticides, people, and unvented combustion processes, such as tobacco smoking and cooking with gas stoves. Organic compounds are also produced indoors from chemical reactions of e.g. ozone with some organic compounds in the air or different materials. Outdoor air is normally the main source of indoor ozone, other sources include ozone generators (marketed as air cleaners), electronic air cleaners (they produce unintentionally ozone as a by-product), and some office equipment (e.g. laser printers).
Some VOCs are odorous and some are suspected causes of adverse health effects. Typical symptoms caused by VOCs include sensory irritation, allergy and asthma, and to the latter related respiratory symptoms. However, typically found concentrations of VOCs in normal buildings are so low that they are not likely to cause either sensory irritation symptoms or respiratory symptoms. On the other hand, it is also evident that indoor air is quite a complex field to study and more research is needed to establish any concrete relationship between concentrations of single or multiple VOCs and adverse health effects caused by them. On the other hand, formaldehyde may be already in quite low concentrations harmful. It may cause sensory irritation and has been classified as a human carcinogen. SVOCs have gained more interest over the last years, since they are suspected to be more detrimental to human health than VOCs. Some SVOCs are suspected to be so called Endocrine Disrupting Chemicals, EDC, i.e. they may disrupt the hormone production of the body.
How do then paints affect indoor air quality? Water-borne paints are typically less harmful than solvent-borne (alkyd) paints, since they release smaller amounts of VOCs. Another disadvantage of solvent-borne paints is that during their drying mechanism usually a substantial amount of new compounds, i.e. compounds not added to the product during its manufacturing, is formed. These compounds include aldehydes and acids, some of which may cause adverse health effects. The VOCs released from water-borne paints origin from the typically small amounts of solvents added to the paint as a film-forming agent, and from film formers and paint additives where the origin is the residual monomers from the polymers used.
The VOC levels of paints are controlled both at the European level and by national guidelines. On the European level the paints should conform to the EU VOC-directive, Directive 2004/42/EC, where the amount of VOC in the wet paint is limited. National guidelines in e.g. Finland, Denmark, and Germany limit the amount of VOCs released from the paint film after a certain amount of time.
Thus, paints release VOCs into indoor air, especially when they are still fresh. The amounts that are released are controlled both by the EU legislation, and in some countries also by national guidelines. When paint is applied to a substrate it wets the substrate a little, which may give rise to additional VOCs. But, when the paint film has dried, it typically releases only very small amounts of VOCs, and may also act as a buffer for compounds originating from the substrate. A dried paint film may act as a sink for VOCs in the indoor air, i.e. it collects VOCs to its surface and can release them later on. Another aspect concerning indoor air quality and paints is that by using paints you enhance the cleaning of surfaces, since they usually make cleaning easier compared with e.g. wall paper due to their better scrub resistance, and thus help to achieve a better IAQ".
Many thanks Leif for this very informative piece.
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