One of the most common questions we’re asked is ‘what’s the difference between LSF (Low Smoke & Fume) & LSNH (Low Smoke Non-Halogen) and why should I care?’ The simple answer is that we should care. It’s all about safety, of both people and equipment. Here at Webro, we pride ourselves on being totally transparent. We understand the materials that we use in our products, and we never compromise on them. Ahead of outlining the key differences between, this is a breakdown of the acronyms that you’ll come across in the market, with a brief explanation of the material and some of its benefits: SEE 'ACRONYM GUIDE' TABLE BELOW
There’s still the misconception that LSF & LSNH are the same material, but as alluded to above this couldn’t be further from the truth. Let’s explore this in more detail.
LSF – Low smoke & fume
This material is essentially a modified PVC, which when burnt releases acrid black smoke. When mixed with water it creates hydrochloric acid (HCL), which is incredibly harmful to people and equipment. It’s generally understood that a good LSF material releases around 15% HCL emissions, whereas a poorer quality material releases up to 22%. Both are relatively high percentages and vary between manufacturers.
If cables that contain LSF materials are installed in a public building there’s a significant risk to life. Black smoke and HCL gas are considered to be more deadly to people than the flames themselves. Once the smoke is inhaled it mixes with moisture in our bodies and hydrochloric acid is created, which irritates our lungs causing coughing, shortness of breath, and eventually loss of consciousness. The risk from smoke created when LSF materials are burnt can’t be understated. It should be duly noted that there are no standards to clarify LSF material quality or performance. As such, they’re open for self-classification by manufacturers and distributors.
LSNH - Low Smoke Non-Halogen
Low Smoke Non-Halogen By contrast, LSNH materials are made up of materials that don’t give off nasty halogens when burnt, so as a result they’re much safer for people. To be classed as non-halogen, the material must give off less than 0.5% HCL gas when burnt. It’s also designed to produce white/light grey smoke, which makes it easier to evacuate heavily populated buildings, maintaining critical visibility of escape signage and keeping evacuation routes clear. The materials are ideal for use in public buildings such as schools, hospital, airports, and railway stations where population densities are high, making escape more challenging. LSNH materials are also relevant to CPR classification — to understand how they relate to cable classes, see our CPR class cables guide. To be classified as LSNH the material must pass rigorous tests. The first is a smoke generation test that determines how much light is lost in a smoke-filled room. Visibility mustn’t drop below 60%. Secondly, a halogen gas emissions test determines the degree of acidity of gases emitted during combustion. It measures the pH level and conductivity.
For CPR compliant LSNH cable options, browse Webro's B2ca and Cca Belden alternative cables — all manufactured to LSNH construction.
What we do here at Webro
Because of the diverse market segments that Webro serves, we cater for many options. The LSF cables that we stock are considered as slightly better than PVC. They’re flexible and easy to handle, but we wouldn’t suggest they’re installed in public buildings where evacuation may be difficult. We would also never suggest that our LSF cables are halogen free. The LSNH cables that we stock and supply are genuinely LSNH throughout. No corners are cut using cheaper PVC or LSF materials on the inside whilst dressing them in a LSNH jacket. This is counterproductive to how the products need to perform in a fire. We always use LSNH materials inside and out, ensuring that all products are tested to confirm suitability. If you’re ever in doubt about the products you’re buying, ask for a specification sheet from your cable supplier to check what’s on both the inside and the outside.
For more information on how LSNH cables relate to CPR classification, read our CPR class cables guide.
If you have any questions about LSF, LSNH or LSHF cables or need help selecting the right cable for your installation, our technical team is here to help. Get in touch online, call us on 0115 972 4483 or email sales@webro.com
Acronym Guide
Article written by Gary Banfield, Technical Lead at
Webro Cables & Connectors, with over 25 years of
experience in the cable industry.
