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Detecting dangerous airborne asbestos particles is difficult because these
particles are very similar to much safer glass or gypsum fibres. But the
University of Hertfordshire in Hatfield claims to have found the answer (GB 2
333 835). Its researchers have exploited the fact that a magnetic field will
affect the asbestos particles because they contain large amounts of iron. In
their detector, a suction pump draws suspect air past an electromagnet, a light
source and an optical detector. When the fibres are aligned by the air stream
they do not scatter light. But if the magnet pulls any fibres out of alignment,
they scatter light onto the detector and an alarm goes off.