14
Fig4
Fig. 5
Ducting
The ducting used should be rigid circular pipe and must be
manufactured from fire retardant material, produced to BS 476 or DIN
4102-B1.
Wherever possible utilise rigid circular pipe which has a smooth
interior, rather than the expanding concertina type ducting. The
lengths of ducting with minimal eect on performance are as follows:
• 4 metres with 1 x 90° bend.
• 3 metres with 2 x 90° bends.
• 2 metres with 3 x 90° bends.
Longer ducting can be used but the performance of the extractor will
likely be reduced. Noise may also be aected by the type of ducting.
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