Freshly renovated or newly built, and it smells: of paint, of adhesive, of "new". Behind this are usually VOC, volatile organic compounds, that off-gas from fresh building materials. Unlike the classic old-building pollutants, VOC are not a legacy of past decades; they arise precisely when something is renovated or newly built. Usually the smell is unpleasant but temporary, and it disappears over time. Sometimes not.
VOC comprise hundreds of substances, among them formaldehyde, toluene, xylene, styrene and limonene. They off-gas from paints, varnishes, adhesives, floor coverings, furniture and sealants.
Where VOC come from
- Paints and varnishes: even products labelled "low-solvent" off-gas measurably in the first weeks.
- Floor coverings and adhesives: vinyl, laminate, parquet adhesive and sealers.
- Furniture: particleboard and MDF are the main source of formaldehyde.
- Insulation and assembly foams: for example PU foams.
- Silicones and sealants: fresh silicones release acetic acid (the typical vinegar smell) or oximes as they cure.
Many VOC decline markedly in the first weeks. Other sources, above all formaldehyde from wood-based materials, off-gas for months to years, because the substance is continually reformed from the binder of the panels (WECOBIS).
When VOC are a problem
Not every smell is dangerous. What should be taken seriously, however, are persistent complaints after a renovation: headaches, dizziness, irritated mucous membranes, nausea or difficulty concentrating (UBA).
The most critical single substance is formaldehyde. The International Agency for Research on Cancer (IARC/WHO) classifies it as carcinogenic to humans (Group 1), on the basis of nasopharyngeal cancer and leukaemia (IARC 2012). This classification describes the hazard of the substance, not the risk in a particular room: the indoor reference value is 0.1 mg/m³ (100 µg/m³) as a half-hour mean, derived by the WHO and adopted in 2016 by the German Committee on Indoor Air Guide Values (WHO 2010; AIR 2016); it is set so strictly at the sensory irritation of the mucous membranes that it also protects against the long-term effects including cancer and carries a safety margin. Ordinary dwellings lie below it, so a temporary new-build smell is not a cancer verdict. It becomes serious where a strong source keeps supplying. For infants, small children and pregnant women, the irritant effect and cancer risk weigh more heavily; especially for a child's room in a new build or freshly renovated space, it is worth reducing the burden before moving in and, in case of doubt, measuring. Why formaldehyde is regarded as unequivocally carcinogenic and where the classification was disputed is set out in the first fold-out.
For experts, or those who want to become one: Why formaldehyde is Group 1, the two cancers and the reference value
Formaldehyde is a reactive gas that acts right at the point of contact. The older and firmer part of the cancer classification is nasopharyngeal cancer: for the nasopharyngeal carcinoma, IARC already saw sufficient evidence in humans in 2006, from cohorts of occupationally exposed workers, and classified formaldehyde as Group 1 on that basis (IARC 2006). The site of action fits the chemistry: the reactive gas first strikes the mucous membrane of the upper airway.
The second, longer-disputed part is leukaemia. It is disputed precisely because of this chemistry: a gas that reacts quickly right at the point of contact barely reaches the distant bone marrow, where the mostly myeloid leukaemias arise, in unchanged form, which makes a simple mechanism hard to explain. In 2006 the evidence for leukaemia was regarded as "strong but not sufficient"; in the reassessment in 2012 IARC concluded that formaldehyde also causes leukaemia, resting above all on the cohort of the US formaldehyde industry and Chinese studies (IARC 2012). This second classification was the narrower one and the one debated within the Working Group; for practical handling at the low concentrations of an indoor space it is secondary, because the reference value is anchored at the far more sensitive mucous-membrane irritation anyway.
The reference value of 0.1 mg/m³ as a half-hour mean hangs on exactly that. The WHO derives it from the sensory irritation threshold: a value that prevents irritation of the mucous membranes in the general population, in its assessment also prevents the long-term effects including cancer (WHO 2010). The German Committee on Indoor Air Guide Values adopted the same value in 2016, which should not be exceeded even briefly over 30 minutes (AIR 2016). Because the value is anchored at the most sensitive effect, it is strict: it is not a threshold for cancer, but a precautionary irritation protection that covers the cancer protection as well.
How high the burden is: the TVOC value and its limits
For the sum of all volatile compounds, the TVOC value serves as an orientation, not as a health limit. Roughly: up to about 0.3 mg/m³ the air is hygienically unobjectionable, a value of 1 mg/m³ should not be exceeded permanently, and from about 3 mg/m³ there is a need to act (UBA; Seifert 1999). The decisive thing is how to read it: the TVOC value lumps chemically very different substances into one sum and is not toxicologically justified. For individual substances such as formaldehyde, therefore, separate, health-based reference values apply that take precedence over the sum assessment. In Austria there is no binding statutory limit for VOC in dwellings, and neither is there in Germany. The Austrian assessment framework is the Richtlinie zur Bewertung der Innenraumluft (guideline for the assessment of indoor air), drawn up by the indoor-air working group (Arbeitskreis Innenraumluft) at the responsible federal ministry with the participation of the Austrian Academy of Sciences; it contains guide values for individual substances such as formaldehyde and a dedicated part on the VOC sum parameter (BMLUK). Alongside it, the reference values of the German Committee on Indoor Air Guide Values and the WHO are used. How the sum assessment is built up in detail and what is changing in the regulation is in the fold-out.
For experts, or those who want to become one: The TVOC concept, the five hygiene levels and the new EU emission limit
The TVOC value (total volatile organic compounds) is the sum of the volatile organic compounds in the room air over a defined boiling range. The German assessment concept assigns it to five hygiene levels (Seifert 1999): level 1 up to 0.3 mg/m³ (hygienically unobjectionable, target value), level 2 above 0.3 to 1 (still unobjectionable, provided no individual substance exceeds its reference value), level 3 above 1 to 3 (conspicuous, permanent use only tenable for a limited time), level 4 above 3 to 10 (objectionable, only short-term use) and level 5 above 10 (unacceptable). The value is explicitly not a toxicologically derived limit, but a hygienic orientation; if an individual substance exceeds its own reference value, this individual assessment always takes precedence over the sum.
To be distinguished from this is the emission from the product. Low-emission building products are assessed in a test-chamber procedure following the scheme of the Committee for the Health-related Evaluation of Building Products (AgBB); on this the quality marks build by which such products can be recognised: EMICODE EC1 and EC1PLUS of the GEV, the Blue Angel and natureplus. Newly added is an EU-wide binding emission limit for formaldehyde from articles: the REACH Regulation (Annex XVII, Entry 77, inserted by Regulation (EU) 2023/1464) limits the formaldehyde release in the test-chamber test to 0.062 mg/m³ for furniture and wood-based materials and 0.080 mg/m³ for other articles; it has applied since 6 August 2026. This is a limit for the release from the product, measured in the chamber, not a limit for the concentration in the room air; the two quantities must not be confused.
How VOC are determined
For persistent complaints, a room-air measurement gives information. An accredited laboratory breaks down the individual substances with their concentrations and forms the TVOC sum; formaldehyde is determined separately and assessed against its own reference value. A low TVOC value therefore does not rule out a formaldehyde burden. From the overall profile the source can often be narrowed down, so that targeted action is possible instead of replacing everything.
What to do
- Ventilate intensively: in the first weeks after a renovation, burst ventilation, several times a day for a few minutes, is the most effective immediate measure. Before moving into a new build it helps to heat and ventilate for a few weeks, because higher temperature accelerates the off-gassing. This clears out the temporary solvent VOC quickly.
- Recognise permanent sources: ventilation does not end what is continually reformed. Formaldehyde from particleboard and MDF off-gases for months to years; here it is not airing out that helps, but the choice of material or the replacement of the source, especially in a child's room.
- Narrow down the source: if the complaints do not ease after weeks, a room-air measurement narrows down the source.
- Material choice: for future work, low-emission products off-gas considerably less, recognisable by marks such as EMICODE EC1, the Blue Angel or natureplus.
With VOC, unlike with the legacy pollutants, the burden comes not from the old stock but from what has just been installed. Which pollutants are to be expected in which construction era is summarised in our overview by construction year; under old parquet, by contrast, PAH-containing adhesive often waits.
Sources
- AIR (2016): Committee on Indoor Air Guide Values (Ausschuss für Innenraumrichtwerte, Germany), reference value for formaldehyde in indoor air: 0.1 mg/m³ (100 µg/m³), not to be exceeded even briefly over 30 minutes, in line with the WHO. umweltbundesamt.de
- BMLUK (Arbeitskreis Innenraumluft): Richtlinie zur Bewertung der Innenraumluft (guideline for the assessment of indoor air). Drawn up by the Arbeitskreis Innenraumluft at the responsible Austrian federal ministry (today BMLUK) with the participation of the Austrian Academy of Sciences; guide values for, among others, formaldehyde and the VOC sum parameter. bmluk.gv.at
- IARC (2006): Formaldehyde, 2-Butoxyethanol and 1-tert-Butoxypropan-2-ol. IARC Monographs, Vol. 88. First classification of formaldehyde as Group 1 on the basis of nasopharyngeal cancer. publications.iarc.fr
- IARC (2012): Formaldehyde. In: Chemical Agents and Related Occupations, IARC Monographs, Vol. 100F. Confirmation of Group 1 (nasopharyngeal cancer) and classification as a cause of leukaemia. ncbi.nlm.nih.gov/books/NBK304432
- Seifert (1999): B. Seifert, Guide values for indoor air: the assessment of indoor air quality with the aid of the sum of the volatile organic compounds (TVOC value). Bundesgesundheitsblatt 42:270 to 278; five hygiene levels, TVOC as an orientation and not a health value. umweltbundesamt.de
- UBA: Federal Environment Agency (Umweltbundesamt, Germany), indoor air: volatile organic compounds (VOC) and TVOC assessment, symptoms and sensitive population groups. umweltbundesamt.de
- Regulation (EU) 2023/1464: amendment of Annex XVII of the REACH Regulation, Entry 77 (formaldehyde). Emission limit in the test-chamber test 0.062 mg/m³ (furniture and wood-based materials) and 0.080 mg/m³ (other articles), applicable since 6 August 2026. eur-lex.europa.eu
- WHO (2010): WHO Guidelines for Indoor Air Quality: Selected Pollutants. World Health Organization, Geneva. Formaldehyde short-term guideline 0.1 mg/m³ (30 minutes) to protect against sensory irritation, which at the same time protects against long-term effects including cancer. ncbi.nlm.nih.gov/books/NBK138711
- WECOBIS: Ecological building-material information system (BMWSB/BAK), VOC and formaldehyde from wood and wood-based materials; sustained formaldehyde release from the binder over years. wecobis.de
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