PVC softens below 90°C and this raises the issue of compliance with AS 1530.4, BS 476.24, AS 1668.1 and BS 5599.9 requirements whereby during the fire test, a smoke extraction duct cross-sectional area must not reduce by more than 25%. 

LAF has tested 78 mm of Vermiduct installed over a 750 x 750 PVC duct to successfully achieve a 3 hr fire resistance level to AS 1530 Part 4.

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