Tar cardboard containing PAH caused odor problems and headaches

naphtalene found in the air of two classrooms

Naphtalene found in the air of two classrooms

Measurement results showed a pollution with naphthalene

In a primary school in Saxony (Germany), odor problems had arisen in two classrooms and in the staff room since the building was renovated. When a new rector took office in 2018, the matter really got going. Ms. Rubens (name changed) not only had a sensitive nose, but increasingly complained of a headache as soon as she was in the staff room. The school administration informed the city administration as the responsible cost bearer. The local building authority then commissioned an engineering office to investigate the indoor air. The measurement results showed a clear pollution of the room air with naphthalene. Since even the guideline II of the German Federal Environment Agency was exceeded with 20 µg / m³, no lessons were allowed to take place in the rooms from now on. A review of the construction plans showed that the school was built in 1964. Therefore, the experts consulted assumed that the building was contaminated. The energetic renovation in 2017 had obviously exacerbated the smell problem. The airtight facade and the lack of controlled ventilation ensured that the pollutants in the indoor air could accumulate more.

The problem was hidden under the screed

The expert removed a total of twenty drill cores from the two classrooms and the staff room. Sixteen of the twenty samples showed tar-containing material. Apparently, in the 1960s, the builders had put the tar cardboard as a barrier layer on the concrete ceiling and applied the screed over it. The material examination in the laboratory confirmed the suspicion. The tar paper contained a considerable amount of polycyclic aromatic hydrocarbons, abbreviated PAH. Naphtalene is the volatile part of the PAH. At a relatively low boiling point of 218 degrees Celsius, this substance can get into the room air through joints and cracks. The smell is described as typically tar-like and is reminiscent of old wardrobes with moth balls.

Sampling and analysis of polycyclic aromatic hydrocarbons

The entire group of pah consists of several hundred individual substances. This high number cannot be managed when analyzing indoor pollutants. That is why in Germany the sixteen combinations of substances from PAH, which the American Environmental Protection Agency (EPA) has defined, have been adopted and are called EPA-PAH. In addition, benzo (A) pyrene (BaP) was defined as the lead substance. In the meantime, however, laboratories and experts have recognized that BaP is not always balanced in the building materials examined. For this reason, the analysis led to undervaluations in individual cases and consequently to incorrect assessments during the remediation of contaminated sites. As a result, a combination test has established itself as the standard for indoor air measurement. The 16 EPA-PAH substances mentioned above are sucked in from the room air via PU foam and glass fiber filters. All sixteen substances can be quantified separately. As a control, naphthalene is determined as a volatile substance using the Tenax method. Otherwise there is a risk that naphthalene cannot be adequately captured via PU foam. Orientative measurement of house dust also enables two variants. The detailed laboratory procedure determines all 16 EPA-PAH; the shortened analysis only evaluates the lead substance benzo (A) pyrene, with the risk of undervaluation mentioned above.
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