You tear out old parquet and underneath there is a black, tar-like layer. Stop. This could be PAH-containing adhesive — one of the most unpleasant surprises in old-building renovations.
Polycyclic aromatic hydrocarbons (PAH) are a group of over 100 compounds consisting of fused carbon rings. They form during incomplete combustion and are found in coal tar — a material that was extensively used as adhesive and sealant between the 1950s and 1980s.
Where PAH Are Found in Old Buildings
In the Austrian buildings we inspect, we find PAH almost always at the same locations:
- Parquet adhesive: The black layer under old strip parquet. Tar-containing adhesive can contain up to 50,000 mg/kg PAH — this is extreme hazardous waste. Especially common in buildings from the 1950s–1970s.
- Roofing felt and sealants: Tar-containing membranes on flat roofs and in basements.
- Tar coatings: Black coatings on basement masonry as moisture barriers.
- Cast asphalt screeds: In some old buildings as a floor substrate.
The typical indicator: you see black, tar-like material and smell a characteristic tar odour — sometimes also a mothball-like smell (that is naphthalene, the most volatile PAH).
Why PAH Are a Problem
PAH are not only a problem in the material. They off-gas over decades and accumulate in household dust. Benzo[a]pyrene, the most well-known individual compound, is classified by the WHO as a Group 1 carcinogen — definitively carcinogenic.
In the body, PAH are converted by the liver into water-soluble metabolites. In the process, highly reactive intermediates (epoxides) are produced that bind to DNA and can trigger mutations. The lungs, skin, and bladder are primarily affected.
The risk is dose-dependent. Intact, sealed parquet floor over PAH adhesive: manageable. PAH adhesive lying open in living areas: action required. And when sanding, milling, or ripping out without protective measures: acute danger.
How We Detect PAH
We take a material sample — a small piece of the suspected adhesive or sealant. The sample goes to an accredited laboratory, where it is analysed by GC-MS (gas chromatography-mass spectrometry) for the 16 EPA PAH compounds.
The decisive values are the benzo[a]pyrene content (BaP) and the total PAH sum. In Austria, tar-containing materials are classified as hazardous waste when they fulfil the hazard-relevant property HP 7 (carcinogenic). In Germany, the classification is more specifically regulated: from 50 mg/kg benzo[a]pyrene or 1,000 mg/kg total PAH, material is classified as hazardous waste (LAGA M20). Tar-containing parquet adhesive typically exceeds these values by ten to fifty times.
PAH analysis is quoted after the initial consultation — scope depends on sample type and required detection limits. Result in 5–7 business days.
If indoor air exposure is suspected (you can smell tar, you live above open PAH adhesive), we can also arrange an indoor air measurement for naphthalene and other volatile PAH.
What You Should Do
Before renovation: If your building was constructed before 1980 and you want to remove old floor coverings — have it checked first. A sample costs a fraction of what a subsequent PAH remediation costs.
PAH adhesive found: Do not sand, mill, or rip out yourself. The dust spreads throughout the entire apartment and deposits in household dust. Professional removal means: containment, negative pressure, HEPA extraction, protective equipment. In Austria, the provisions of the GKV (Limit Values Ordinance) apply.
Floor intact and no odour: No immediate action required. Document and factor in during the next renovation.
Costs of PAH remediation: Professional removal of PAH adhesive typically costs €80–€180/m², depending on area and accessibility. That sounds like a lot — but it is calculable. What is not calculable: the costs when you discover after unsupervised ripping-out what you have released.
When You Should Get in Touch
You are planning a floor renovation in an old building? You see black layers under the parquet? You can smell tar in the apartment?
PAH is only one of the pollutants that appear in old-building renovations. In buildings from before 1990, asbestos is also often found in floor coverings and adhesives (→ Recognizing Asbestos), and in buildings from before 1970 lead is frequently found in paints and pipes (→ Lead in Old Buildings).
We come to you, assess the situation, and take samples if needed. Within a week you have certainty.
15-minute initial consultation, free of charge.