VOCs (Volatile Organic Compounds) are organic, carbon-containing compounds that evaporate even at low temperatures. In many cases, VOCs are largely harmless to living beings - despite their influence on well-being. However, this group of substances also includes substances that are critical to health, such as formaldehyde.
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The English abbreviation VOCs (Volatile Organic Compounds) refers to the group of carbon-containing substances that evaporate at low temperature or already appear in a gaseous state at room temperature. These "volatile organic compounds" are also divided into two subgroups. The VVOCs (Very Volatile Organic Compounds) describe very volatile and often odour-intensive substances. The less volatile organic compounds are called SVOCs (Semivolatile Organic Compounds).
The TVOCs (Total Volatile Organic Compounds), i.e. the totality of these substances, are in a boiling range between 50 °C and 250 °C. The decay time can be between 10 days and up to 3 years.
Among the best-known representatives of VOCs are formaldehyde and solvents such as toluene.
Since these are organic compounds, they can appear in all areas of life and are harmless to living beings in most cases. However, an increased concentration indoors can considerably reduce well-being.
In Germany, there has so far only been a legal stipulation of limit values for workplaces that are particularly polluted in terms of production technology. For hygienic reasons, however, the Federal Environment Agency has now issued recommendations for the presence of VOCs. The guideline values comprise several levels ranging from hygienically harmless (below 1 mg/m³ - below 150 ppb) to hygienically conspicuous (between 1 and 3 mg/m³ - 150 to 1300 ppb) and hygienically questionable (between 3 and 10 mg/m³ - 1300 to 4000 ppb) to hygienically unacceptable (above 10 mg/m³ - above 1500 to 4000 ppb). In addition, guideline values have been defined for individual gases in the VOC group.
Many legally relevant sources mention mg/m³ as the unit. What is measured, however, is a mixture of many substances with different molecular masses, whose volume fraction in the air is given in ppb (parts per billion) or ppm (parts per million). This discrepancy results in conversion margins for substances with low and high molecular weights.
An increased concentration of VOCs can initially manifest itself through altered odour and taste perception or irritation of the eyes or mucous membranes. Other noticeable effects include poor concentration, exhaustion, dry skin, eczema and headaches. These symptoms are also known as sick building syndrome and describe acute exposure. The higher the concentration of VOCs in the indoor air, the more strongly the odour perception and the mucous membrane irritations are affected.
The toxicity of the individual substances differs greatly. Nevertheless, scientists fear chronic sequelae in the case of long-term exposure. These include carcinogenic, mutagenic and reproductive effects.
Medical experts also see a connection between VOCs and the increase in allergic reactions, especially in infants and young children.
So far, however, a detailed scientific investigation is still pending for many VOCs.
In the formation of VOCs, a distinction is made between biogenic (i.e. natural) and anthropogenic (i.e. man-made) sources. Natural sources include the emission of organic products through the metabolism of all living organisms, as well as putrefaction and other biological decay processes. Reactions of natural materials, such as wood or oils, also contribute to the accumulation of VOCs in the air we breathe.
Synthetic sources of VOCs include the evaporation of numerous building materials (varnishes, paints, carpets, insulation materials, etc.) as well as the use of solvents, cleaning products or cosmetics. Combustion processes, e.g. tobacco smoke, fireplaces and stoves or cooking, can also contribute to the accumulation of VOCs in indoor spaces.
Volatile organic substances are measured by means of a resistive sensor. Molecules that "dock" on the surface of the sensor cause a change in the electrical resistance in the sensor. The advantage of our sensor is the individual sensitivity calibration by the manufacturer and the only very low cross-sensitivity to temperature and humidity.
Cross-sensitivities are the (desired) main feature of the measuring principle. The VOC sensor is calibrated for alcohol (ethanol), but also reacts to aldehydes, ketone, hydrogen, methane and others - an all-rounder.
As a particularly powerful and comprehensive measuring instrument for indoor air quality, the air-Q air analyser is also equipped with a sensor that can measure VOCs or volatile organic compounds.
You can find a lot of information about the technology of the meter here. You can order the air-Q in the air-Q Shop.