N was employed by V to make up wiring harnesses for motor vehicles. After April 1997 this work involved soldering, an operation which was potentially hazardous because soldering gave off fumes containing colophony, a toxic substance. N claimed that exposure to colophony caused her to develop industrial asthma and she claimed compensation on the basis of breach of the employer’s duty under regulations 6 and 7 of the 1994 Regulations. At first instance, her claim succeeded. The employers appealed to the Court of Appeal.