Odor emissions from materials and olfactory assessment of indoor air

Material odors and unexpected odor impressions in indoor environments can cause irritation and raise health concerns among users. Manufacturers of construction products and materials for vehicle interiors therefore strive to optimize the odor of their products to prevent user discomfort. Assessment schemes for building products, such as the AgBB scheme or the criteria for the Blue Angel label, include optional odor assessments. The results of the odor assessments can be declared in addition to the mandatory product information.

In the automotive sector, vehicle manufacturers also set requirements for the odor behavior of materials and components.

Since neither sensors nor analysis technology can replicate human odor perception, material odors are evaluated by human panels. Depending on the requirements, these persons can be trained or untrained in odor evaluation. Trained persons undergo regular training in odor perception and are able to describe odor impressions qualitatively.

For reliable evaluations of the odor intensity, a standardized reference scale is used. Before the odor evaluation, the test subjects are presented with defined acetone concentrations in the air to help them calibrate their perception. These concentrations correspond to discrete PI values (PI = perceived intensity, a numerical indicator of perceived intensity). Only people who have successfully completed this calibration participate in the odor evaluation.

Indoor air quality is assessed using a category scale (“imperceptible” to “extremely strong”) since transporting a calibration reference for on-site testing is not possible.

In addition to odor intensity, the acceptance and hedonic odor effect are also used to assess material and indoor air odors. They can also be tested and evaluated as part of an intensity assessment.

Olfactory assessments by subjects do not provide any information about the substances responsible for a specific olfactory impression. To determine the odorants, materials are stored in odor-free glass containers under controlled conditions. A defined volume of air is collected from the headspace above the material sample and analyzed using gas chromatography-mass spectrometry combined with human olfactometry. The substances contained in the air sample are separated by chromatography, reaching the end of the separating column at a different time. Alongside the mass spectrometric detector, a trained person identifies the substances exiting the separation column. If the chromatographic properties and the odor quality match the entries in the IBP's proprietary odorant database, the odorant is considered to be identified. This method also allows for a semi-quantitative determination of the odorants.