Table of contents
Introduction
When designing indoor wiring systems, safety is more than just mechanical strength. LSZH SWA Cable Safety refers to the ability of a cable to emit reduced smoke and zero halogen gases in the event of a fire. While not fireproof, this property makes Low Smoke Zero Halogen (LSZH) Armoured Cables vital for maintaining visibility and limiting corrosive fumes during evacuation and firefighting. Compliance with BS 7671 Wiring Regulations [1] ensures these cables are used appropriately.
Why LSZH Matters – LSZH SWA Cable Safety
The main benefit of LSZH cables is reduced smoke and the absence of toxic halogen emissions. Traditional PVC-sheathed cables release thick smoke and corrosive gases, which can obscure escape routes and damage sensitive electronics. By contrast, LSZH cables minimise these hazards, making them the safer choice for:
- Public buildings such as hospitals, schools, and offices.
- Enclosed areas such as tunnels, underground stations, and car parks.
- Industrial facilities where equipment damage from corrosive fumes must be avoided.
Note: Doncaster Cables describe this as LSNH (Low Smoke Non-Halogen) in their datasheets, but it is the same classification as LSZH (Low Smoke Zero Halogen).
PVC or LSZH: Two Sheath Options
Modern Armoured Cable Range is available in two sheath types:
- PVC SWA – the standard choice for most outdoor, industrial, and domestic installations where fire performance is not specified.
- LSZH (or LSNH) SWA – required in public buildings, transport hubs, tunnels, or enclosed spaces where reduced smoke and zero halogen emissions are critical.
- Note: Doncaster Cables datasheets use LSNH (Low Smoke Non-Halogen), which is the same classification as LSZH (Low Smoke Zero Halogen).
- 2-Core LSZH SWA, 3-Core LSZH SWA, 4-Core LSZH SWA, 5-Core LSZH SWA, and 7-Core LSZH SWA.
All are rated at 600/1000V with an operating temperature of -15°C to +90°C.
Installation Considerations – LSZH SWA Cable Safety
While LSZH SWA offers fire performance benefits, it must still be installed to best practice standards:
- Maintain correct bend radii to prevent sheath damage.
- Route cables away from high-risk mechanical areas or use additional protection.
- Terminate with appropriate glands and earth tags/banjos to ensure armour bonding.
- For indoor junctions, use enclosures that preserve both IP rating and fire integrity.
Common Applications – LSZH SWA Cable Safety
- Office blocks and commercial buildings with high occupancy.
- Transport infrastructure such as rail stations and airports.
- Data centres and control rooms where equipment must be protected from corrosive gases.
- Multi-storey residential buildings where safe evacuation is critical.
Quick Selector
- Need maximum mechanical protection? Choose SWA.
- Need both protection and reduced smoke? Use SWA LSZH.
- Working in public or enclosed buildings? LSZH is strongly recommended.
- Domestic outdoor wiring? Standard SWA may suffice.
FAQs – LSZH SWA Cable Safety
Is LSZH SWA fireproof?
No. LSZH does not make the cable fireproof — it reduces smoke and halogen gas release, making evacuation safer and limiting damage.
Where should LSZH SWA be specified?
In public buildings, transport hubs, and confined spaces where smoke and toxic gas would pose significant hazards.
Does LSZH affect performance?
No. LSZH SWA has the same voltage rating and mechanical strength as standard SWA, with the added benefit of safer emissions.
Can LSZH be used outdoors?
Yes, LSZH SWA can be installed outdoors, but it is most commonly specified indoors or in enclosed areas where smoke safety is the priority.
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References
[1] BS 7671 Wiring Regulations – IET
[2] IBA Buying Group
[3] Electrical Distributors’ Association (EDA)
[4] Electrical4Less Reviews
[5] Doncaster Cables – SWA LSZH (BS 6724) Datasheet: (internal source)
Low Smoke and LSZH SWA Cables: Meeting Safety Standards Indoors