Low Smoke Zero Halogen Cables from Prysmian Cables UK


Low Smoke Zero Halogen Cables from Prysmian Cables UK


Low Smoke Zero Halogen Cables from Prysmian Cables UK

Fire Performance Cables in Buildings
Posted: 20th November 2014

Fire Performance Cables in Buildings

Fires have a high cost in the loss of human life and with a third of fires originating inside buildings the type of cable used can be crucial.

In Europe, fire death rate figures in 2003 and 2004 were equivalent to 30.000 deaths per year. In the UK the Department for Communities and Local Government stated:

"the most commonly identified cause of death from a fire incident is being overcome by gas or smoke"

In fact being overcome by gas or smoke accounts for 44% of fire deaths. 

Reduced Escape Times

The Swedish Rescue Services Agency reported the decline in  the average time from start of a fire to flashover from 15 minutes in 1950,  5 minutes in 1985 and now fatal conditions can occur after 3 minutes. This fall in escape time has resulted from the increase in use of plastics in the home.

We can conclude that escape times have reduced due to plastics use and the reduction of smoke and effluent gases will help save lives and benefit rescue teams. This is where low fire-hazard cables can greatly improve safety.

Energy cables used within buildings can be split into typically three classes of fire performance with many common names but few rigid definitions. These names include but are not limited to:

  • PVC cable
  • Low smoke cable
  • Fire resistant cable

Each must perform as a suitable electric cable with the construction and testing details included in the appropriate British Standard to facilitate this. Differences become apparent in how they react to fire, but in this document we will be looking at the first two, PVC cable and low smoke cable.

General Energy cables

General energy cables are designed, specified and installed for general lighting and power distribution inside and outside buildings. Normally PVC sheathed, in the event of fire the sheath will burn to produce dense black smoke and acid gas. PVC cables can also act as a propagating medium and spread flame along the cable and potentially throughout the building. Failure of the cable occurs because cable insulation, sheathing and armour-bedding are combustible materials and melt or burn away.

Dense Smoke

The dense black smoke produced during combustion can inhibit occupants trying to escape the building by disorienting them as well as reducing the effectiveness of emergency lighting systems by obscuring exit signs and routes.

Acid Gases

Acid gases produced by combustion can also hinder evacuation by causing choking and vomiting of those trying to escape. They can damage metallic components in the electronic building services and also the steel members in reinforced concrete structures. This can also increase the time and cost of refurbishment resulting from the fire.

Cables with Low Fire Hazard

This class of cables have a wide range of common names and a broad range of British Standards to describe their performance during fire. Terms such as LSOH or LSFH are manufacturer specific and care should be taken to analyse the exact specification required early in a project to avoid selection of inappropriate cables.

For example, cables described as ‘low smoke’ might be assumed to pass ‘zero halogen’ tests and have flame retardant characteristics. However without confirmation from the manufacturer or supplier this may not be the case.  They are different tests conducted upon different samples at different times.

Energy cables with low fire hazard are typically specified and required as general LV lighting and power distribution in occupied public buildings. They connect everyday services and systems that are not essential to alert, evacuate or manage the fire. In the event of fire and they can reduce the hazard if selected correctly. These cables have 3 main areas where they need to perform:

  • Smoke
  • Acid gas
  • Flame spread

We will look at these in the next post.

Also see What is Low Smoke Cable?

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