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Human nose detects new-car smell

22 April 2004

A smoky car with overflowing ashtrays, which has stood in the sun for a couple of hours, would be ranked ‘5 – Highly unpleasant’ on the Volvo Cars smell test scale. The odour in the passenger compartment of a car is evaluated on an international scale from 1 to 6. The test is carried out using ‘standard’ noses and a sunshine simulator, which is capable of shining as brightly as the Mediterranean sun even in the darkest Nordic winter.

As yet, there is no technical device which can replace the human nose or, in particular, determine if something smells good or bad. For this reason, Volvo Cars has established a ‘smell test panel’ consisting of eight specially selected people with ‘standard’ noses, who guide the designers in their choice of materials and production methods, especially for the interior of the car. A new Volvo must smell like a Volvo!

What smells good or bad is a subjective judgement. Some people may regard a certain odour as offensive, whereas others may think it is pleasant. Some people like strong odours, whereas others think them unpleasant regardless of the actual smell.

"However, a strong smell may also irritate a hypersensitive individual," says Lotta Styrenius, a Volvo Cars concept engineer specialising in smell. "In this case, he or she may develop a headache, irritation of the eye, nose or throat, or may feel ill."

Solvents, additives and monomers in plastics are the main sources of odours in the interior of a car. How the interior trim details should smell is the task of the ‘smell test panel’.

The panel consists of eight people who undergo a careful selection process to ensure that they all have a ‘normal’ sense of smell and do not differ appreciably from each other in this respect.

"People who like an odour that others in the panel think is unpleasant are eliminated," explains Lotta Styrenius, "likewise those who either cannot detect or are hypersensitive to smells. All must be non-smokers, since smoking can affect the sense of smell."

The panel evaluates the smell from the interior trim items on a scale from 1 to 6, on which ‘1’ indicates ‘Not noticeable’ and ‘6’ is ‘Unbearable’. To secure approval, the test ranking must not exceed ‘3’, which is ‘Clearly noticeable, but not yet unpleasant’.

"We impose strict demands both on ourselves and our suppliers," comments Lotta Styrenius. "Travelling in a car should be a pleasant  experience for the nose as well."

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