Lastly there’s Low Smoke Halogen Free, LSHF for short (or any other of its many pseudonyms that you may care to use). When burnt, LSHF cable produces only small amounts of light grey smoke and miniscule amounts of HCl, which as a result greatly increases a person’s chances of escape from a burning building in which it’s installed. The reason LSHF products react so differently when exposed to fire in comparison to PVC & LSF cables is the complete absence of PVC. The outer sheath and conductor insulation of these products are often made from polyethylene which contains little by way of chlorine, and low chlorine means low HCl. For a cable to carry the LSHF tag it’s subjected to a number of additional tests over and above those carried out on PVC/LSF variants, two of which are briefly detailed below:
EN 50267-2-1 stipulates that emissions of HCl must not exceed 0.5%
EN 60684-2 stipulates that during the burning process light transmittance must not fall below 60%, or put another way visibility should not be reduced by more than 40%
Additional tests detailed in BS EN 50525-1 with respect to permissible levels of acidity, conductivity and fluorine produced through the process of burning must also be carried out on LSHF flexible cable.
Compare the values above to those of PVC mentioned previously and the difference is marked, with visibility being reduced by up to 90% and HCl emissions being as high as 30%. LSF fairs slightly better, but not to any worthwhile degree when compared to LSHF.