Introduction

The abbreviation VOC (Volatile Organic Compounds) refers to the group of volatile organic compounds. VOC describes gaseous and vaporous substances of organic origin in the air. These include, for example, hydrocarbons, alcohols, aldehydes and organic acids. Many solvents, liquid fuels and synthetically produced substances can occur as VOCs, but also numerous organic compounds formed in biological processes. Many hundreds of different individual compounds can occur together in the air.

Experts distinguish VOCs from Very Volatile Organic Compounds (VVOCs) and Semivolatile Organic Compounds (SVOCs). The sum of the concentrations of all VOCs gives the TVOC value (Total Volatile Organic Compounds).

Urban pollution

VOCs as air pollutants are a result of incomplete combustion of fuels, are formed during combustion or are due to evaporation. Some industrial processes and the use of solvents result in

What are the sources of VOCs in indoor air?

VOCs originate from very different sources. Biological processes can be external air sources, for example plant metabolism, decay and degradation processes. Other outdoor air sources are technical processes in which substances are produced from incomplete combustion (especially motor vehicle exhaust gases) or as volatile by-products from industrial and commercial processes.

Possible indoor sources are products and materials for building construction and interior decoration e.g.

• floor, wall and ceiling materials
• paints,
• varnishes
• adhesives
• furniture and decorative materials

Also important are:

• care products
• cleaning products
• hobby products
• tobacco smoking
• even food preparation and
• human metabolism

Compared to outdoor air, indoor air sources in Central Europe generally have a much greater health significance, as people are mainly in buildings. In addition, the distance to VOC sources indoors is usually smaller. VOCs from outside air can also enter the interior. As a rule, however, ventilation reduces the original indoor concentrations.

How do VOCs get into the air?

When solvents or liquid fuels evaporate and liquid or pasty products dry, large quantities of VOCs escape into the ambient air. Less obvious is the spread of different by-products that are not firmly embedded in products. They can be slowly released from the product surface into the air and continuously supplied from the inside of the product to the surface (material emission). This applies, for example, to residual solvents and building blocks in plastics (monomers), auxiliary substances such as plasticizers, solubilizers, antioxidants, stabilizers and catalysts from the production process, as well as accompanying substances such as fragrances, flame retardants and biocidal agents. Typical VOCs are also terpenes, which are released into the air from materials and products of natural origin, such as wood. VOCs are also produced as reaction products, for example between oxygen, ozone or water containing natural substances, such as those found in wood and vegetable oils.

Strong odors in new or recently renovated indoor environments are often due to off-gassing from new building materials, finishes or furnishings. VOCs may come from treated or engineered wood products, carpets, flooring, cabinets, paints, stains, varnishes etc.

What are the health effects of VOCs?

Usually the individual VOC concentrations are very low and there is no need to worry about health effects.  Several Environment Agency have compiled representative overviews of the VOCs found in apartments.

Concentrations which cause health impairments can occur immediately after construction and extensive renovation measures, as well as with improper processing and massive use of less suitable products.

Odour nuisances, irritations and symptoms that cannot be directly attributed to a disease have been described as acute effects on humans.

These effects must be avoided, as must possible chronic effects which scientists have derived from toxicological assessments; especially naturally carcinogenic, mutagenic and toxic to reproduction effects. If such effects of substances are known, they may generally no longer be used in the end product (Chemicals Prohibition Ordinance). However, it cannot be completely ruled out that VOCs with such potential effects are contained in traces in the product if they were present in uncontrolled precursors or recycled materials. A working group at the Federal Environment Agency has developed guideline values for indoor air for some frequently occurring VOCs that are particularly important to health.

Short-term health effects can be:

• headache
• nose, throat, eyes inflammation
• coughing, painful breathing
• skin irritation

Long-term health effects can be:

• cardiovascular diseases
• respiratory diseases (asthma, cancer)
• inpacts on liver, spleen, blood
• affects on the central nervous system (headache, anxiety)

Evaluation, guideline and limit values

Selected VOC limit values in Germany (D), France (F) and California (CA)(Oppl & Neuhaus, 2008).

How can VOCs be reduced?

When something smells, it is more than likely emitting TVOCs. Even good smelling things like perfume or air fresheners have negative effects!

If applicable and necessary, regularly replace air filters in indoor fan systems and refresh your home (open windows).

Lessen sources of VOCs, store all known toxic products like heavy cleaning supplies, paint, varnishes,  etc. separate from your home in a shed or external garage. Avoid buying VOC products in bulk and try to reduce the amount of products you purchase that contain VOCs. Try to purchase environmentally friendly products with lower levels or no VOCs.

How do we measure VOCs?

At Aristoteles Consulting, we measure TVOCs with continuously registering measuring devices. This devices are equipped with a Photo Ionisation Detector (PID) sensor. The measured data are saved by a data logger, which can be read out after the measurement to get information about the concentration and to create data tables and graphs showing time dependent variations.

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