Emissions of Volatile Organic Compounds (VOCs)

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Toxic pollutants of volatile organic compounds (VOCs) are given off by a number of common home and office products as well as building materials. VOCs are a group of chemicals based on the carbon atom (organic) that evaporate rapidly (volatile). A common example of VOCs is formaldehyde, which is in high concentration in board-based wood furniture, foam-backed carpet, and paint preservatives.

In general, VOCs act as irritants, causing symptoms such as watery eyes, sneezing, or coughing. Some allergy sufferers develop a specific immune response to VOCs. In severe case, VOCs may even trigger an asthma attack. As a general rule, the higher the VOC content in a product, the stronger is its odour.

Some naturally occurring VOCs include the citrus fragrance of an orange or the eye-stinging vapour given off by an onion when it is cut.

The evaporation of VOCs into the air (known as “out-gassing” or “off-gassing”) may occur rapidly and disperse quickly, as when you cut into an orange; or it may occur slowly over many months from products such as board-based furniture. This slow leakage helps to contribute to the background level of VOCs found within the typical home and office.

People with allergy should avoid using products that emit VOCs. In case they have to be used, allow sufficient time for the new products (e.g. new carpet, new painting) to off-gas before close contact with them. They should be placed in well ventilated places to keep the indoor concentration as low as possible.

Common products that emit VOCs

Printer and copier emit VOCs and other hazardous particles

Printer and photo-copier are commonly used in both home and office environments. When toners are heated to the temperatures in the fusers, they release hazardous materials including volatile organic compounds, ozone, aldehydes / ketones, inorganic gases, and minute toner dust particles. The toners are the primary source of organic emissions from these machines.

Recent studies show that indoor office concentrations of certain Hazardous Air Pollutants (HAPs) - styrene, ethylbenzene, and the xylene isomers - can exceed a total of 200 µg/m3 in the copier room, and 20 µg/m3 in the surrounding office space. The general office levels caused by the photocopier are about twice of that in outdoor air; the copier room levels are 20 times of that in outdoor air.

In the office, printers, fax, photo-copiers etc should ideally be put in a separate room with good ventilation away from the working cubicles.

VOCs emissions from electronic products with printed circuit board (PCB)

Many electronic products today use printed circuit board as one of the essential components. These include personal computers (PCs), telephone, fax machines, and photocopiers, TV, Hi-Fi, ovens, microwave ovens, rice cooker etc. Volatile organic compounds are emitted from the printed circuit board during use and cause allergic reactions and other adverse health effects in humans.

Off-gassing from these products with PCB is most prominent during the initial break-in period when electrical heating occurs. This is especially true in the case of PC monitors, the internal operating temperatures of which can range from 60 to 70 °C at full power.

Solvent Content of paints and varnishes release VOCs

Most paints used for walls are water based, while those used for woodwork could be either oil or water based. Oil-based paints contain much higher concentrations of solvents, which are used to thin the oil for easy application, hence more likely to cause allergy problems. Some oil paints may contain more than 50% solvent. As the paint dries, the solvents evaporate into the air, initially at high concentrations. It is advisable for allergy sufferers to use water-based paints and varnishes for walls and woodwork. These are usually low-odour and dry more quickly than oil-based paints.

Wood preservatives and board-based wood products

Wood preservatives are used to protect wood from insect or fungal attack. Many of them are solvent-based and release VOCs that may trigger allergic reactions for some people. These chemicals should be handled with care to avoid direct skin contact or breathing in the fumes.

Wood preservatives may cause irritation of the skin and mucous membranes, as well as headaches, dizziness, and nausea. It is better to use water-based wood preservatives which contain much lower levels of VOCs instead of oil-based ones.

Board-based wood products are widely used for flooring, shelving and especially flat-packed kit furniture. However, some of these fabricated wood products contain high concentrations of formaldehyde and will out-gas for months, or sometimes years, even though at much lower levels than the initial phase. Even low concentrations of formaldehyde in the air may irritate the eyes, nose and throat, particularly in people with rhinitis or asthma, and may cause running eyes, sneezing and coughing.

It is advisable to use furniture made of solid wood instead of board-based wood. This is becasue solid wood usually contains natural preservatives, therefore there is no need to add artificial ones that emit VOCs.