Volatile Organic Compounds are a group of volatile organic chemicals that vapourises easily and immediately when exposed to air, even in room temperature, and are considered pollutants which means that they are hazardous to human and animal health. They can be both naturally and synthetically occurring compounds. These are highly volatile chemicals, i.e. they have a low boiling point which causes it to vapourise easily i.e., causing large numbers of the molecules to evaporate from the liquid or solid form of the compound and enter the surrounding air. As a primary group of pollutants, with indoor concentrations generally higher than outdoors.
EPA, US, defines VOCs as: “any compound of carbon, excluding carbon monoxide, carbon dioxide, carbonic acid, metallic carbides or carbonates, and ammonium carbonate, which participates in atmospheric photochemical reactions”.
Types of VOCs:
Some of the most common VOCs include benzene, acetone, ethylene glycol, formaldehyde, methylene chloride, perchloroethylene, toluene, xylene, and 1,3-butadiene, and tetrachloroethylene. There are three distinct groups of Volatile Organic Compounds (VOCs). These differ based on the boiling point of each chemical; they include:
- Very Volatile Organic Compounds (VVOCs) – Formaldehyde and Acetaldehyde
- Volatile Organic Compounds (VOCs) – Benzene, Toluene and Xylenes
- Semi Volatile Organic Compounds(SVOCs)
Sources of VOCs
According to an EPA report on the environment, VOCs are emitted from a variety of sources, including motor vehicles, chemical manufacturing facilities, refineries, factories, consumer and commercial products, and natural (biogenic) sources (mainly trees). At indoor spaces, these chemicals are usually found into various products used in construction of the building – like paints, solvents, adhesives, varnishes, vinyl floors – and in daily used products such as cleaning chemicals, air fresheners, cosmetics, fuel oil, upholstery fabrics, carpets and moth balls in huge concentrations. At any given time, there could be fifty to hundreds of individual VOCs functioning indoors.
They can be produced by dry cleaning, cooking, smoking, using some non-electric space heaters, photocopying or printing, using wood burners, and from electronic devices, stored paints and chemicals.
Formaldehyde, one of the most common VOCs, is a colorless gas with an acrid (sharp and bitter) smell. It is common in many building materials such as plywood, particleboard and glues. Formaldehyde can also be found in some drapes and fabrics and in certain types of foam insulation.
VOCs can be released from products during use and even in storage. However, the amount of VOCs emitted from products tends to decrease as the product ages.
