When interior surfaces turn blotchy dark within a short period of time, this is referred to as fogging, also known as the fogging effect or "black flat". The effect often affects newly renovated rooms and occurs almost only during the heating season. The deposits, which occur especially above radiators and on the inside of exterior walls, have a sooty-greasy consistency. According to the current status, these are deposits of semi-volatile organic compounds (SVOCs, e.g. plasticizer compounds, fatty acids and fatty acid esters) that can escape from carpets, laminates, PVC floor coverings, woodchip wallpaper, but also from plastic surfaces, paints and varnishes, which accumulate and deposit on surfaces, especially in poorly ventilated interiors. However, several influencing factors play a role in the development of fogging , the exact influences and interactions of which have not yet been conclusively clarified.
According
to the current status, fogging is not hazardous to health, as long as it is ensured that it is actually fogging and not, for example, mold spores. Nevertheless, the dark coatings naturally pose an aesthetic problem.
As a preventative measure, it is recommended to use solvent- and plasticizer-free interior paints, often declared as "free of fogging-active substances", in conjunction with regular and intensive ventilation, especially after renovation work.
If black discoloration is present, contacting an environmental or health authority, the involvement of an expert and/or fogging measurements by an environmental analysis laboratory can help.
Source: bauwion
