The substances involved in the formation of the black deposits come from different products into the living spaces. These products were mostly brought into the rooms by different people (residents, building operators, craftsmen). As a rule, these people cannot be accused of any culpable behavior, as they do not know that the products may be involved in the formation of the black deposits. To date, there are few suppliers on the manufacturer side who label problem substances on their products – such as plasticizers. Since presumably not every plasticizer-containing product promotes the formation of black deposits, most manufacturers see no need to label the content of their products – for example, with regard to plasticizer content.
But there are also positive examples: Some well-known wall paint manufacturers have offered for some time now paints that are clearly labeled as “solvent- and plasticizer-free.” The environmental label “Blue Angel” is also an important indicator for consumers for targeted product selection. Especially if one has already had a problem with black dust deposits in the apartment, care should be taken upon renovating again to use only low-problem products. Although this alone does not guarantee that the black deposits cannot reoccur (due to the complex formation process), experience shows that the problem usually does not occur again with targeted product selection during renovation and intensive ventilation for several weeks after completion of the renovation work.
Is there a health risk?
According to current knowledge, black dust deposits do not pose an immediate health risk. The concentrations of problem substances – low-volatility organic compounds, such as plasticizers – are only slightly elevated in the affected apartments compared to non-affected apartments. According to current knowledge, the concentrations are significantly below the threshold of a possible acute health hazard. Nevertheless, as a precaution – not to mention the “aesthetic” problem of the unsightly apartment – it is advisable to clarify the causes and remove the deposits. However, if the deposits show elevated concentrations of polycyclic aromatic hydrocarbons (“PAHs”) or soot (both arise from combustion processes), a health risk may be present.
Removal of the damage
Before starting to remove the deposits by cleaning or by renovating again to “eliminate” them, one should get to the root of the causes of the pollution. It is not necessarily required to eliminate all influencing factors that have contributed to the formation in each individual case. Usually, it is sufficient to eliminate individual factors. For example, when renovating again, one can choose a wall paint that is solvent- and plasticizer-free. In individual cases, a change in heating behavior can also help.
Eliminating structural defects (thermal bridges) helps to prevent the deposits from preferentially settling in such places. Also, the sparing use of candles and oil lamps can alleviate the problem. Intensive wet cleaning with detergent additives, plastic cleaners, and similar products is often required to remove the deposits. Simply painting over usually does not help against the smudgy deposits. During the cleaning processes, affected wallpapers, for example, may be so damaged that they must be completely removed. In individual cases, floor coverings must also be removed or larger structural interventions (reduction of thermal bridges) must be carried out. However, such extensive measures should only be considered if the “simple” renovation steps (use of solvent- and plasticizer-free paints, intensive ventilation after renovation, avoidance of sooting candles, etc.) have not been successful. To clarify in individual cases, besides on-site inspections by experts and evaluation of questionnaires, chemical analyses in the affected apartments are also considered. Such analyses are only meaningful if suspicion of a “fogging” phenomenon has already been confirmed by the on-site inspection and the formation of the deposits is not from a very long time ago. Analysis is also always recommended if it is unclear whether the deposits are black dust deposits or soot residues from combustion processes (or both).
Never again black deposits?
The problem of the “black apartments” is not yet finally solved as long as we do not know the concrete contribution of
• the behavior of the residents (ventilation, heating, use of candles, etc.)
• the condition of the building, and
• the composition of the products used.
As long as the underlying cause-effect processes there have not yet been clearly deciphered, we can only take preventive action. This means, for example:
• Use of low-emission products,
• Elimination of building defects, and
• Proper heating and ventilation.
Initial steps have already been taken on the product side to reduce the occurrence of substances in indoor air that can promote the phenomenon: Various paint manufacturers have been offering “solvent- and plasticizer-free” products for some time. This should in future also be extended to other products intended for indoor use from which the mentioned problem substances can off-gas.