Cologne, Germany óFord Motor Co., a team of human smell-testers, a $75,000 computerized "electronic nose," and a row of household canning jars ensure that while customers enjoy that "new car" smell, no unacceptable odors come from a car's interior.
The electronic nose produced by EEV/CSS (formerly Neotronics Scientific) uses an array of 12 chemical sensors, each of which responds to different components within an aroma to produce a "fingerprint" that identifies the material under test. Each sensor has a polymer surface that acts as a conductor between two electrodes. The polymers react with the aroma molecules in an air sample, varying their electrical resistance.
Potential auto interior materials undergo a standard process, designed to simulate real-life conditions in a car on a hot, humid day, which is when smells are most noticeable. Samples of the materials are sealed in airtight containers, and heated to 40C for 16 hours.
A panel of seven people evaluates each sample for smell for a few seconds and rates it on a four-point scale. One point means no smell detected, two means a smell is detectable but it would be acceptable to the customer, three is unacceptable, and four is disgusting! If the result is an overall rating of two or less, the material is judged acceptable.
Other applications for the electronic nose include checking water quality at breweries and establishing freshness of fish. Such sensors can differentiate between one- and three-day-old fish, and are just as discriminating in identifying good and bad samples of automotive materials.