Smoke Density Testing for Cables
Cable Smoke Density Testing to BSEN 61034 (previously BS EN 50268) is commonly known as the 3 metre cube test. It is designed to determine the volume of smoke generated when cables are burned.
The Cable Smoke Density Test is primarily performed on Low Smoke Zero Halogen cables, and is conducted inside a custom-built chamber measuring 3 metres wide by 3 metres deep by 3 metres high - hence the three metre cube test name.
Over a period of 40 minutes the cables are burned whilst a beam of white light crosses the chamber. A fan is used to circulate the air, mimicking a fire scenario. The smoke density test monitors the transmittance of this light with a minimum 60% light visibility being required for LSZH cables.
Smoke density testing isn't usually conducted on PVC cables as when subjected to fire the cable sheathing and insulation materials emit large quantities of toxic fumes and light obscuring black smoke which would completely cloak the white light beam.
This test can also be used to assess LSF Low Smoke Fume cables, although as these are often constructed with a PVC variant they can often produce similar volumes of smoke to standard PVC.
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