Fire performance of construction products is an essential element to be taken into account in the context of fire safety for building design. PVC cables represent an excellent choice when considering their fire performance, reaching up to B2Ca class, and d0 and s1 subclasses, under the EU CPR Regulation.
DISCOVER THE SCIENCE BEHIND PVC CABLE SAFETY
Studies and tests show that, due to its intrinsically self-extinguishing characteristics, PVC is difficult to ignite and does not sustain combustion.
The presence of chlorine in the polymer structure makes PVC ignitability rather difficult, even in absence of any flame retardant. This explains why, contrary to many other materials, there is no sustained lateral flame spread.
Furthermore, thanks to the charring properties of PVC, there are no flaming droplets with PVC products. Under standardised test conditions, in which the sample is forced to burn, PVC typically generates a dense smoke. However, in a real fire situation, when PVC products do not completely burn or represent a small part of burnt materials, the smoke contribution from PVC is generally not so relevant.
Unlike odourless toxic gases, such as carbon monoxide that is by far the most hazardous element in a fire, the presence of hydrogen chloride generated by PVC combustion can be detected at totally harmless trace levels, due to its distinctive smell. As such, the emission of HCl (hydrogen chloride) gas at an early stage of fire acts as a ‘warning’ signal to people to evacuate the area immediately.
CONTINUED INNOVATION TO MAKE PVC CABLES EVEN MORE FIRE SAFE
New formulations for PVC cables are currently under development to further improve their performance in fires. Flame Retardant Low Smoke (FRLS) PVC compounds developed by PVC4Cables are already available and widely utilised for manufacturing FRLS cables. These compounds achieve a B2ca classification, with performance tested in accordance with EN 50399 under the Construction Products Regulation (CPR). They are notable for significantly reducing smoke production and minimising toxicity, with carbon monoxide (CO) emissions comparable to those of halogen-free flame retardant (HFFR) cables.
Additionally, new Low Smoke Acidity (LSA) PVC compounds have been developed to further limit the release of hydrogen chloride (HCl) during combustion. LSA PVC cables exhibit even lower CO emissions compared to HFFR alternatives. They also meet high standards, achieving a Bca classification and s1b rating for smoke production, as demonstrated through testing conducted under EN 50399.
FIRE PERFORMANCE ENHANCED WITH MCCP ALTERNATIVES
One promising area of research involves increasing the halogen content in PVC formulations to further enhance flame retardancy. This includes replacing Medium-Chain Chlorinated Paraffins (MCCPs) with bio-based chlorinated esters developed by PVC4Cables Partner Altair Chemical.
These innovative alternatives offer comparable flame retardancy and thermal stability while significantly improving performance in critical fire tests, such as the EN 50399 (CPR) burning test. By carefully optimising the chlorine content with these new materials, manufacturers can achieve both enhanced flame resistance and reduced environmental impact, including lower migration rates and smoke emissions, all while maintaining compliance with regulatory standards.
ADVANCES THROUGH NANOTECHNOLOGIES
Nanotechnologies, too, represent an interesting perspective for the development and use of efficient functional additives in polymers. Experimental work show that positive effects at nanoscale level are evident even with a limited amount of additives in several features, combining chemical effects on thermal stability, degradation and HCl evolution with improved or unmodified physical performances.
PVC4Cables is funding strong R&D in low smoke acidity compounds, and actively disseminating data through scientific journals, conferences, and webinars.
PVC ADVANTAGES IN CASE OF FIRE
PVC cables can reach B2Ca class, and d0 and s1 subclasses, under the EU CPR Regulation
PVC is difficult to ignite and does not sustain combustion
PVC is self-extinguishing
PVC does not contribute to flame propagation
PVC does not generate sparks or flaming droplets
PVC irradiates only a minimum amount of heat
PVC would generate very little smoke in a real fire situation
PVC expands by up to 800% and carbonises in the external layer (like a meringue) when it is burned, thus making a significant contribution to slowing down fire propagation
The smoke released from PVC combustion is not more toxic than the one released from any other carbon-based material, including natural materials such as wood
Hydrogen chloride (HCl) contained in the smoke is irritating and provides an immediate signal of the development of the fire, acting as an escape alarm
UNDERSTANDING CORROSION AND FIRE RECOVERY
The role of PVC cables in fire scenarios is often misunderstood, particularly concerning the potential costs of corrosion versus the broader impact of fire damage. While some continue to raise concerns about corrosion costs associated with PVC, real-world data from fire incidents suggests that the primary cost drivers lie elsewhere.
Annually, post-fire damage reach vast sums in Europe and beyond, with the majority attributed to smoke removal rather than corrosion caused by hydrogen chloride (HCl) emissions. In actual fire conditions, factors such as high temperatures and smoke are the predominant causes of damage. HCl’s contribution is relatively minor compared to the immediate threats posed by intense heat and carbon monoxide (CO) levels, which often escalate before HCl reaches concentrations capable of causing significant corrosion.
PVC cables, especially those with Flame Retardant Low Smoke (FRLS) properties, are specifically designed to minimise smoke density during fires. This characteristic significantly reduces post-fire clean-up costs and limits the overall damage caused by smoke. While HCl-related corrosion is a consideration, it remains secondary in importance during fire recovery efforts. Critical threats like the spread of flames and smoke inhalation risks occur long before corrosion effects become relevant.
In many cases, injuries, fatalities, and extensive property damage arise because the fire grows too large to control or extinguish. The selection of cables with higher fire resistance classifications, such as B2ca or Cca, over Dca- or Eca-rated cables, offers improved safety and performance. These higher-rated cables are better suited to maintaining the continuity of business operations and conserving property during fire events.
By investing in advanced PVC cable technologies, industries can better mitigate fire risks, reduce recovery costs, and ensure safer environments.
REGULATORY FRAMEWORK
To be considered safe, electric cables installed in any type of construction or engineering work, need to comply with essential safety requirements. All cables must be placed on the European market as CE marked with an available Declaration of Performance. Safety requirements are listed in two EU regulatory documents:
THE LOW VOLTAGE DIRECTIVE
THE CONSTRUCTION PRODUCTS REGULATION
The Construction Products Regulation (Regulation (EU) No 305/2011, CPR) sets the harmonised technical conditions for free circulation of products within the European Union and identifies a number of essential requirements to respect, including reaction-to-fire performance of products in the event of an outbreak of fire.
Following the publication of the products standards and of all the necessary supporting standards related to test methods and classification, the CPR basic requirements related to safety in case of fire for construction works came fully into force for cables on 1 July 2017.