‘It's an ill wind that blows nobody any good,’ says the old adage, and a case in point is that of polyvinylchloride, a thermoplastic material with great corrosion resistance which, although produced in the laboratory nearly 100 years ago, has only been of commercial importance since the last war. In the manufacture of any fan the emphasis is on design. No matter what material is being used, no fan, however well constructed, can do its job efficiently unless it has been well designed, and here experience is useful. It is a relatively simple matter to fabricate a fan from plastic material, but the accumulation of experience and ‘know‐how’ to make the fan an efficient machine can only be gained by many years of work in the fan manufacturing industry.