5 Must-Have Features in a low smoke zero halogen lszh

1. Introduction to LSZH Conduits

In today’s world, the demand for safer, more sustainable construction materials is growing rapidly. One such innovation revolutionizing the electrical industry is LSZH conduits, which stands for Low Smoke Zero Halogen conduits. These conduits are designed to prioritize safety and environmental considerations without compromising performance.

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When traditional PVC conduits burn, they release harmful halogens and thick smoke, posing serious health risks and complicating evacuation during emergencies. In contrast, LSZH conduits are engineered to emit minimal smoke and no toxic halogen gases during combustion, making them a preferred choice for safety-critical applications.

1.1 The Importance of Material Innovation

Material innovation plays a crucial role in modern electrical conduit systems, especially as industries face stricter safety regulations and growing expectations for sustainability. LSZH conduits exemplify how advancements in material science can meet these challenges head-on. They provide solutions to long-standing problems associated with traditional materials, such as smoke toxicity and environmental impact.

This post aims to showcase why LSZH conduits are superior to traditional PVC conduits by exploring their unique characteristics and key benefits. From enhanced fire safety to eco-friendly properties, LSZH conduits are a forward-looking solution for industries that value safety, compliance, and sustainability. By the end of this article, you’ll have a clearer understanding of how LSZH conduits can redefine safety standards in various applications.

2. What Are LSZH Conduits?

Low Smoke Zero Halogen (LSZH) conduits are a type of electrical conduit material specifically engineered to enhance fire safety in various environments. They are designed to offer superior performance compared to traditional PVC conduits, primarily by reducing harmful emissions during a fire and ensuring safer conditions for evacuation and firefighting operations. In this article, we will explore what LSZH conduits are, how they work, and why they are increasingly preferred in critical environments.

2.1 Definition and Composition of LSZH Materials

LSZH conduits are made from materials that produce minimal smoke and no halogen gases (such as chlorine, fluorine, and bromine) when exposed to fire. These materials are usually thermoplastics that contain inorganic fillers, most commonly aluminum trihydrate (ALTH), which helps in fire retardation. When exposed to high temperatures, ALTH undergoes an endothermic reaction that absorbs heat and releases water vapor (steam). This process helps to cool the surrounding area, disrupt combustion, and form a protective char layer that prevents the spread of flames.

This composition makes LSZH conduits not only fire-resistant but also significantly safer than traditional conduits. Unlike standard materials, LSZH conduits produce no toxic or corrosive gases, and their low smoke density helps maintain visibility and breathable air during a fire. These features make LSZH materials crucial in spaces where safety is paramount, such as public transportation systems, healthcare facilities, and offshore platforms.

2.2 Understanding LSZH, LSOH, and Other Names

LSZH (Low Smoke Zero Halogen) and LSOH (Low Smoke Zero Halogen) are terms often used interchangeably, but they are closely related in terms of their properties. Both refer to materials used in electrical conduits and cables that produce minimal smoke and no halogen gases when burned, significantly enhancing safety during a fire.

LSZH (Low Smoke Zero Halogen): This term refers to materials that emit a low amount of smoke and are free from halogenated compounds (such as chlorine, fluorine, bromine, and iodine). These materials are commonly used in environments where fire safety is critical, such as public transport systems, hospitals, and high-rise buildings. The absence of halogens ensures that toxic gases like hydrogen chloride or hydrogen fluoride are not produced during combustion, which can otherwise cause severe health risks.

LSOH (Low Smoke Zero Halogen): LSOH is essentially another way to refer to LSZH materials. In many cases, these terms are used interchangeably, especially in the context of cable and conduit products. LSOH materials offer the same benefits as LSZH, such as low smoke density and the prevention of halogen gas emissions during combustion. The terminology difference often comes from regional preferences or specific industry standards.

Other name for reference:

Zero Halogen (ZH): Refers to materials that are free from halogens, minimizing toxic gas emissions during fires.

Low Smoke Halogen-Free (LSHF): Highlights both low smoke emission and the absence of halogens, often used in public infrastructure.

Low Smoke Zero Halogen Free (LS0HF): Emphasizes low smoke and halogen-free properties, commonly used in critical environments like nuclear plants.

Halogen-Free (HF): Describes materials without halogens, often paired with other fire-safety features like low smoke or flame retardance.

Flame-Retardant Low Smoke (FRLS): Combines flame resistance and low smoke emission, used in high-risk applications like aerospace.

Fire-Resistant, Low Smoke (FRLS): Focuses on materials that resist fire and emit minimal smoke, ensuring continued operation during fires.

Non-Halogenated (NH): Refers to materials free of halogen compounds, often low-smoke, but requires verification of other fire-safety features.

Polymeric Low Smoke Zero Halogen (PLSZH): Materials made from polymers that are both low in smoke and free of halogens, offering flexibility and fire safety.

3. Key Characteristics of Low Smoke Halogen Free Conduits

3.1 How LSZH Conduits Emit Less Smoke During Combustion

One of the standout features of Low Smoke Zero Halogen (LSZH) conduits is their ability to produce significantly less smoke during combustion compared to traditional materials like PVC. This characteristic is crucial for maintaining visibility and ensuring the safety of individuals during emergencies, especially in environments where evacuation or firefighting operations may be challenging.

When materials burn, they release smoke as a byproduct of the combustion process. The composition of the material, including its chemical makeup and the presence of various fillers, plays a significant role in determining how much smoke is produced. In the case of LSZH conduits, these materials are specially designed to emit minimal smoke when exposed to fire.

Aluminum Trihydrate (ALTH): A key component of LSZH materials is aluminum trihydrate (ALTH), an inorganic filler used to enhance fire resistance. When LSZH conduits catch fire, the ALTH undergoes an endothermic reaction, absorbing heat and releasing water vapor (steam). This steam disrupts the combustion process, preventing the material from burning as easily and reducing the smoke generated.

Zero Halogen Emission: Traditional materials like PVC release halogen gases when they burn, which contribute to the formation of dense, toxic smoke. LSZH materials are free from halogens, meaning they do not emit harmful gases like chlorine, bromine, or fluorine. This halogen-free nature prevents the generation of thick, opaque smoke that can make it difficult to see during a fire, which is a significant safety risk in confined spaces.

Char Formation: In addition to producing steam, the aluminum trihydrate in LSZH conduits also helps form a char layer on the surface of the material during combustion. This char layer acts as a protective barrier, reducing the spread of fire and further limiting smoke emissions. The char traps particulates and prevents the release of additional smoke and gases into the environment.

3.2 Why Halogen-Free Composition and Materials Matter for Safety

The composition of a material plays a significant role in determining its behavior during a fire. One of the standout features of Low Smoke Zero Halogen (LSZH) conduits is their halogen-free composition, which directly impacts their safety and performance in fire situations.

The term “halogen” refers to a group of chemical elements in the periodic table that includes fluorine, chlorine, bromine, iodine, and astatine. These elements are commonly used in manufacturing various products, including plastics, cables, and coatings, due to their ability to enhance certain properties like flame resistance. However, the presence of halogens in materials, especially when exposed to fire, poses significant safety hazards. In contrast, halogen-free materials, such as LSZH (Low Smoke Zero Halogen) materials, are designed to eliminate these dangers, offering a safer alternative in fire-prone environments.

Halogens are often added to materials as flame retardants to reduce the risk of ignition. When exposed to high temperatures, halogens can react with other compounds in the material, forming free radicals that inhibit the combustion process. This helps to delay the ignition of the material. However, the benefits of halogens in flame retardancy come at a significant cost during a fire:

Toxic Gas Emissions: When materials containing halogens, like PVC (Polyvinyl Chloride), catch fire, they release harmful gases such as hydrogen chloride (HCl), hydrogen fluoride (HF), and hydrobromic acid (HBr). These gases can be toxic, corrosive, and extremely dangerous to human health and the environment. For example, hydrogen chloride, when mixed with moisture (such as in the respiratory system), forms hydrochloric acid, which can cause severe damage to the lungs and eyes.

Corrosive Effects: Halogenated gases are not only toxic but also corrosive, posing risks to both people and equipment. When released during a fire, these gases can corrode metal components, leading to long-term damage to electrical systems, machinery, and other sensitive infrastructure. In environments like data centers, aircraft, and nuclear plants, where sensitive electronics and equipment are crucial, this can be disastrous.

Obscured Visibility: Halogenated materials, especially when burning, produce thick, black smoke that significantly reduces visibility in an emergency. This makes it harder for occupants to escape and for firefighters to navigate the affected area. The dense smoke is not only visually impairing but also harmful to the respiratory system.

3.3 Flame-Retardant Properties of LSZH Conduits

One of the standout characteristics of Low Smoke Zero Halogen (LSZH) conduits is their enhanced fire safety performance, which is largely attributed to their flame-retardant properties. In fire-prone environments, particularly in enclosed or densely populated spaces, ensuring that cables and conduits do not contribute to the spread of fire is crucial. LSZH conduits, with their high level of flame resistance, play a vital role in protecting lives and property during a fire.

LSZH conduits are specifically designed to meet high fire safety standards, making them an ideal choice for installations in areas where fire resistance is a top priority. Unlike traditional PVC conduits, which can burn rapidly and contribute to the spread of fire, LSZH materials are treated to provide excellent flame resistance and slow down the progression of flames.

The flame-retardant properties of LSZH conduits are a result of their carefully engineered composition. LSZH materials typically include inorganic fillers such as aluminum trihydrate (ATH), which serves a dual purpose during a fire. ATH acts as a flame retardant by releasing water vapor and cooling the surrounding area when heated, effectively suppressing the flames and limiting their spread. Additionally, these materials are formulated to form a char layer upon combustion, which acts as a barrier to further flame penetration and helps protect the surrounding structures.

Low Flame Spread: LSZH conduits are designed to resist the spread of flames along their surface, ensuring that fire does not travel rapidly through electrical wiring or conduit systems.

Self-Extinguishing Behavior: Once the source of fire is removed, LSZH conduits tend to self-extinguish more rapidly than traditional PVC, which can continue to burn even after the external flame source has been eliminated.

Reduced Combustion Risk: The combination of inorganic fillers and non-halogenated materials significantly reduces the amount of fuel available for combustion, minimizing the overall fire load and risk of a fire spreading.

3.4 Eco-friendly Composition and Disposal Benefits

As the world increasingly turns toward sustainability, the environmental impact of building materials has become a critical consideration. LSZH (Low Smoke Zero Halogen) conduits stand out as a more eco-friendly option in the electrical conduit market, thanks to their environmentally conscious composition and their role in supporting sustainable building practices.

One of the defining features of LSZH conduits is their halogen-free composition. Unlike traditional PVC conduits, which contain halogens like chlorine and can release toxic gases when burned, LSZH materials are made using non-halogenated materials, significantly reducing the environmental and health hazards associated with their disposal and burning.

Halogen-Free Materials: The absence of halogens, such as chlorine, means that LSZH conduits do not produce toxic gases like hydrogen chloride when they are exposed to fire. In contrast, halogenated materials like PVC can emit poisonous gases such as dioxins and furans, which are harmful to both humans and the environment. By opting for LSZH materials, the potential for pollution from these dangerous substances is significantly reduced, making them a safer choice for both the environment and human health.

Non-Toxic Emissions: When burned, LSZH conduits release significantly fewer toxic fumes compared to traditional PVC. This not only reduces the health risks for individuals in proximity to a fire but also minimizes the environmental damage caused by the release of harmful chemicals into the atmosphere. This makes LSZH conduits a much more environmentally responsible option, especially in areas where air quality is a concern.

Recyclability: Many LSZH materials are designed to be more recyclable than their PVC counterparts. Although recycling infrastructure for LSZH is still evolving in some regions, the absence of halogens and other hazardous chemicals makes these conduits easier to recycle and reprocess. This contributes to the overall reduction of landfill waste and supports a circular economy in the construction and electrical industries.

3.5 Adherence to Global Safety Standards and Certifications

In today’s rapidly evolving construction and electrical industries, adhering to global safety standards and ensuring that infrastructure is future-ready are crucial elements for both safety and longevity. LSZH (Low Smoke Zero Halogen) conduits are increasingly recognized for their ability to meet and exceed these requirements, making them an excellent choice for modern electrical systems.

LSZH conduits are specifically designed to meet the stringent safety regulations that govern building materials and electrical systems worldwide. These regulations ensure that materials used in construction not only perform optimally but also pose minimal risk to human health and the environment. LSZH materials are compliant with various international safety standards and certifications, making them a reliable choice for a variety of industries.

Fire Safety Standards: One of the primary concerns when selecting materials for electrical installations is fire safety. LSZH conduits excel in this area by meeting or exceeding international standards for flame retardancy and smoke suppression. For example, LSZH materials adhere to safety standards like:

• IEC : A standard for testing smoke density in cables and conduit materials.
• IEC -1: Ensures that cables and their sheaths (including conduits) are resistant to flame propagation when exposed to fire.
• UL 94: A widely recognized standard for determining the flammability of plastic materials, ensuring that LSZH conduits do not ignite or burn easily under certain conditions.

Halogen-Free Certifications: As LSZH conduits are halogen-free, they comply with several important standards related to toxic gas emission reduction. The most notable of these certifications are:

• RoHS (Restriction of Hazardous Substances): An important European Union directive that restricts the use of certain hazardous materials, including halogens, in electrical and electronic products. LSZH conduits are designed to meet RoHS compliance requirements, ensuring they are free from harmful substances.
• CE Marking: This certification signifies that LSZH materials comply with European health, safety, and environmental protection regulations.

Environmental Standards: In addition to fire safety and halogen-free certifications, LSZH conduits meet various environmental standards, ensuring they are manufactured with minimal ecological impact. They comply with:

• ISO : This international standard outlines the criteria for an effective environmental management system. Manufacturers of LSZH conduits often adhere to this standard, demonstrating their commitment to sustainability in their production processes.

Building Codes and Industry-Specific Regulations: In many sectors, including the nuclear, transportation, and military industries, stringent regulations govern the use of materials for safety-critical applications. LSZH conduits are frequently specified for use in high-risk environments where fire safety and reduced smoke emissions are paramount. The railway industry and submarine installations, for instance, require materials that comply with DEF STAN 02-711 (UK military standard) and ASTM E662 (for measuring smoke density), both of which LSZH conduits meet.

4. LSZH vs Traditional PVC Conduit, Challenges and Considerations for Conduit Choosing

To provide a quick reference for the key differences between LSZH (Low Smoke Zero Halogen) and Traditional PVC conduits, we have created a comparison table below. This table highlights the features, benefits, and drawbacks of each material to help professionals make informed decisions based on their project requirements.

Feature LSZH Conduit Traditional PVC Conduit Smoke Emission Low smoke emission during combustion, improves visibility and safety in fires High smoke emission, can obscure visibility during fires Halogen Content Zero halogen (no chlorine, bromine, or iodine) Contains halogens (e.g., chlorine), which release toxic gases when burned Toxicity of Gases No toxic or corrosive gases released during combustion Releases toxic gases, including hydrochloric acid and hydrogen chloride Fire Resistance Flame-retardant, helps prevent the spread of fire Flame-retardant Environmental Impact Eco-friendly, less environmental harm due to halogen-free composition Higher environmental impact due to halogen content and greater smoke output Cost Higher cost due to specialized materials and manufacturing process Lower cost, more affordable for large-scale installations

While LSZH (Low Smoke Zero Halogen) conduits offer significant advantages in terms of safety, environmental impact, and regulatory compliance, there are some challenges and considerations that need to be addressed before they can be fully integrated into electrical projects. 

Higher Cost One of the primary challenges associated with LSZH conduits is their higher cost compared to traditional PVC (Polyvinyl Chloride) conduits. The production of LSZH materials involves the use of specialized compounds and additives, such as aluminum trihydrate for flame retardancy, which can make them more expensive. Additionally, the manufacturing processes required to ensure the material’s low smoke and halogen-free properties are more intricate, further driving up the price.

Availability and Supply Chain Considerations LSZH conduits may not be as widely available as traditional PVC conduits, especially in certain regions or specific markets. While demand for fire-safe and environmentally friendly materials is growing, limited supply or reliance on specialized suppliers can sometimes result in delays or increased lead times.

5. Applications of Low Smoke Halogen Free Conduits

Healthcare Facilities: Hospitals and medical centers demand the highest safety standards to protect patients, staff, and critical equipment. LSZH conduits are a preferred choice for these facilities as they reduce toxic gas emissions and smoke during fires, ensuring safer evacuation. Additionally, their non-corrosive properties protect sensitive medical devices and wiring systems, making them indispensable in operating rooms, intensive care units, and emergency power systems.

Data Centers: Data centers house high-value servers and networking equipment, where fire-related damage can lead to catastrophic data loss and operational downtime. LSZH conduits provide superior fire resistance and prevent the spread of corrosive gases, protecting IT infrastructure and maintaining the integrity of data systems. Their adoption ensures compliance with strict fire safety regulations, offering peace of mind to businesses that depend on uninterrupted data access.

Transportation Systems: Modern transportation networks, including railways, subways, and airports, rely on LSZH conduits for their safety and durability. These conduits are used extensively in tunnels, control rooms, and signaling systems. In confined spaces, their low smoke emission and absence of toxic halogens significantly enhance passenger and worker safety, facilitating clear evacuation routes and protecting critical infrastructure.

Residential and Commercial Buildings: In high-density residential complexes and commercial buildings, LSZH conduits are increasingly replacing traditional PVC to meet stricter building codes. They are ideal for electrical and networking installations, as they reduce the risk of fire hazards and contribute to a healthier indoor environment. Architects and contractors prioritize LSZH conduits for green building certifications and future-proofing properties.

Airports: Airports are bustling hubs where fire safety is paramount. LSZH conduits are integral to electrical and communication systems in terminals, baggage handling zones, and control towers. Their low-smoke and halogen-free properties ensure safe evacuation and prevent damage to critical aviation systems, such as radar and navigation equipment, ensuring uninterrupted operations even in emergencies.

Schools and Educational Institutions: Safety in schools and universities is critical, particularly in protecting children and staff. LSZH conduits are widely used in these facilities to minimize risks during fires. They emit less smoke and avoid releasing harmful halogens, ensuring better air quality and visibility for safe evacuations. LSZH conduits also align with sustainability goals, promoting safer and eco-friendlier building practices in education.

Want more information on low smoke zero halogen lszh? Feel free to contact us.

Industrial and Manufacturing Plants: Factories and manufacturing facilities often house flammable materials and high-energy equipment, necessitating robust fire safety measures. LSZH conduits are employed to safeguard electrical wiring in hazardous zones. Their flame-retardant properties reduce the risk of fire spread, while their resistance to corrosive gases ensures the longevity of industrial control systems, even in harsh environments.

6. Conclusion

In today’s rapidly evolving world, ensuring safety and sustainability in infrastructure is more important than ever. LSZH (Low Smoke Zero Halogen) conduits stand out as a critical solution for reducing fire-related risks, protecting human lives, and minimizing environmental impact. Their low smoke emission, halogen-free composition, and enhanced fire safety performance make them an essential choice for industries prioritizing health, safety, and eco-conscious practices.

Ctube is a trusted manufacturer specializing in high-quality PVC conduits and fittings designed to meet the needs of various industries. From PVC conduit like Schedule 40 and 80 conduits to Low-Smoke Halogen-Free (LSZH) conduits for enhanced fire safety, Ctube delivers innovative and sustainable solutions. Our product range includes durable and UV-resistant solar conduits, flexible conduits, and a variety of fittings such as elbows, couplings, and electrical boxes—all rigorously tested for reliability and compliance with international standards like UL, CSA, ASTM, AS/NZS .

Thanks for your reading, and good luck with your projects.

FAQs

1. Can Ctube’s conduits be customized for specific projects?

Absolutely. Ctube offers customization options for sizes, colors, and designs, ensuring that our conduits and fittings are tailored to meet the specific requirements of your project. Whether you’re working on a residential, commercial, or industrial installation, we can provide a solution that fits your needs.

2. Are Ctube’s products certified for safety and quality?

Yes, all Ctube products are rigorously tested and comply with international safety and quality standards, including UL, ASTM, and AS/NZS . We ensure that our products meet the highest performance standards, offering reliable solutions for all your electrical conduit needs.

3. How do I order Ctube products for my project?

You can easily order Ctube products by visiting our website or contacting our sales team directly. We offer competitive pricing and timely delivery for both small and large-scale projects, with full support throughout the ordering process.

Low smoke zero halogen compounds not only deliver greater fire protection performance, they have been constantly evolving so that the number of applications and performance are increasing, while relative cost is beginning to decline.

A number of high-profile fires over the past several decades have served to alert just how dangerous plastics can be when burned. In the King’s Cross fire in the late s, for example, 32 people died in a London underground subway from the toxic fumes. That one incident prompted the U.K. to initiate more stringent standards to prevent halogen-related deaths, even though at that time the cable would not be as flame retardant as PVC jacketed cable.

In addition to fatal fires, the sheer volume of cable that exists today adds fuel to residential, commercial and industrial settings. In response, materials with a high resistance to fire were developed with little performance penalty. Low smoke zero halogen (LSZH) compounds not only deliver greater fire protection performance, they have been constantly evolving so that the number of applications and performance are increasing, while relative cost is beginning to decline.

Before looking at the particulars of LSZH wire and cable compared with the use of PVC-based products, it’s important to wade through the plethora of terms involved.

Acronyms, Common Terms and Misnomers

The industry is quite familiar with such communications cable terms as CM, PVC and LSZH. There are, however, endless terms that mean the same thing, almost the same thing and definitions not even in the same ballpark. Here, then, is a list that might help:

• CM indicates that the cable is National Electrical Code (NEC or NFPA 70) compliant. CM designates use for low voltage communications circuits restricted to one floor.
• CMR, also known as riser-rated cable, is used to prevent fires spreading between vertical installations, when cables are used between floors through risers or vertical shafts.
• CMP, also known as plenum-rated cable, is able to restrict flame propagation to five feet or less, while also limiting the amount of smoke during a fire. It is often installed above suspended ceilings so that air passes through.
• PVC (polyvinyl chloride) is most often associated with CM and CMR-rated cable. Examine the extensive features and characteristics of PVC throughout this paper.
• FEP (fluorinated ethylene polymer) is most often associated with CMP cable. CMP cable may use a low smoke PVC jacket.
• LSZH, LSOH and LSNH indicate by the letters ZH, 0H, OH, HF, NC and NH that the materials used in producing the cable are free of halogen. LS signifies that low smoke materials are used.
• The FR in FRLS and other acronyms indicates the materials improve reaction to fire (low fire). Low-smoke, low-fire and zero-halogen cables must meet IEC standards.

Misnomers? It is often thought that cable designated LSF (low smoke and fume) is the same as LSHF (low smoke halogen free). Low smoke and fume is obviously not as stringent a classification as is LSHF or LSZH, to be consistent in this white paper.

Clearly, when making such a critical decision, engineers must know what it is they’re choosing from, and that they’re getting what they need and also what they are paying for.

The Growing Importance of LSZH

Low smoke zero halogen cable insulation and jacket have no fluorine, chlorine, bromine, iodine or astatine, so they do not emit toxic or corrosive fumes and create minimal smoke when fire is present. LSZH cables feature a flame-resistant jacket that doesn’t emit toxic fumes even if burned.

LSZH cables also feature:

• Non-propagation of fire and flame
• Less dense smoke emission
• IEC standards compliance
• Flame retardant

​Given the absence of PVC, when burned, LSZH cable produces small amounts of light grey smoke and minute levels of hydrochloric acid (HCl), increasing the chance of escape during a fire. Sheath and conductor insulation of the cable can be made from polyethylene, containing little chlorine, so that HCl is not an issue.

A Low Smoke Halogen Free (LSHF) certification from UL indicates that the combustible materials in use are halogen free and also comply with low smoke requirements when tested in accordance with IEC -2. To be designated zero-halogen, the material must have less than 0.2% of halogens by weight. Ensuring compliance involves UL testing, adherence to MIL-C-, acid gas testing to establish a pH level under 3, testing for halogen content, smoke release and acid-gas equivalence.

If LSZH has a downside in addition to a cost premium of approximately 30%, it is not as flexible as PVC and therefore more prone to jacket cracking during installation. Installation may require special lubrication to avoid damage, especially in cold environments. For that reason, it is generally not ideal for robotic or continuous flex applications. Advances in the underlying compound materials and processing continue to lessen some of these issues. ZHTPU is an example of a zero halogen material suitable for robotics.

The Up and Downside of PVC

Polyvinyl chloride (PVC) has been the traditional go-to wiring and cable material for more than 60 years. While it has a long life, is inexpensive to make and features compounds and processes that have gradually improved over the years, it also has some negatives.

When PVC burns, it produces chemicals and dense black smoke, rapidly reducing visibility. Within approximately 10 minutes, visibility is down by 50% and within a half hour, 90%. The result is a dramatic decrease in a person’s ability to escape. However, visibility isn’t the only problem. A burning PVC cable also emits hydrochloric acid and other toxic gases when it burns. Hydrogen chloride (HCl) can represent up to 30% of the emissions. When it is mixed with water, it forms hydrochloric acid, which is toxic as well as corrosive.

When HCl is inhaled, breathing becomes extremely difficult as the lining of the throat swells. If it comes in contact with eyes, it causes irritation all the way to permanent corneal damage. It also damages mucus membranes. Given these physical reactions combined with impeded visibility, it is easy to see why fatalities are high in building fires. In the King’s Cross Station fire, many died from smoke and fume inhalation.

Yet PVC, when not used in an area where there is a high level of humans, has its advantages, including:

• PVCs are inherently resistant to ignition, which may slow down the spread of a fire throughout the building. PVC compounds often include smoke suppression ingredients and additional flame-retardant properties.
• PVC is recyclable so that a high percentage is recycled back into wire and cable.
• PVC is produced using substantially less energy than alternative materials.

Common wire and cable insulation materials include PVC, cross-linked polyethylene (XLPE) and ethylene propylene rubber (EPR). Multiple chemical ingredients are added to provide performance, longevity, flexibility and ruggedness.

LSZH vs. PVC

Both LSZH and PVC cables feature excellent performance. Comparing them side by side, their differences become clear.

The advantage of halogenated flame retardants is that they are cost-effective and reduce the flammability of products without negatively affecting the processing properties of the polymers. Once heated, however, LSZH shines. PVC cable when burned emits toxic chemical fumes and acid. LSZH cable meets both health and safety standards.

Halogen-free wiring is still more complex and expensive to produce, uses more electricity and water in the process, and production is slower than PVC. In comparison, PVC is easier to process. It can be melted and made with a small amount of energy.

In an environment on fire, when visibility is reduced by up to 90% and with high HCl emissions, the difference between the two is even clearer. If the health and safety demands fire-proof cables, LSZH is worth the expense. If not, PVC cables are most likely the solution.

In the future, however, as the cost of LSZH comes closer to parity with PVC, and the attractiveness of being able to offer one cable globally becomes increasingly more important in a standard-centric world, LSZH will most likely begin to replace PVC across the board.

Applications

For most companies currently using LSZH cable, the application represents the deciding factor for the transition from PVC.

Halogen-free cable is intended for use in applications where insulation with low toxicity, low smoke generation and low corrosiveness is necessary, such as:

• Mass transit
• Datacenters
• Aviation
• Industrial environments
• Subways
• Buildings
• Nuclear/Military use
• Shipping
• Wherever human safety and protection of equipment is a primary goal
• In confined spaces with large amounts of cables near humans or electronics

While widespread use exists in Europe, the U.S. has lagged based on expense and performance concerns as well as complex building standards. Historically cable designs in Europe were often unable to pass testing standards prevalent in the U.S.

Applications in cold environments are difficult with LSZH cables, as there is reduced flexibility of the cables based on high additive loading. One advantage is low friction, enabling a move toward jackets that do not require lubrication often used during cable pulls.

Modern data centers, laden with large amounts of cabling and enclosed spaces containing cooling systems, are beginning to move towards LSZH adoption. It is reasonable to expect this trend to continue as the technology’s popularity takes hold based on safety and its environmentally friendly designation.

Insurance companies are also specifying LSZH cable. Globalization of the cable design, often called “dual rated,” will simplify installation, training and logistics. The ability to cover both Europe and North America will be significant.

A Look at Evolving Global Standards

Globally, while European safety standards have concentrated primarily on low smoke and zero halogen (LSZH) cable as well as electrical requirements, standards in the U.S. have focused on fire resistant properties and propagation of flame resistance during fires. In North America, the onus is on meeting building codes where there are more stringent electrical requirements, as well as an emphasis on wet electrical properties.

Given that U.S. and European standards are, in effect, diametrically opposed, it is important for wire and cable suppliers and consumers to have a product that will address a wide range of requirements, while meeting global standards along the way.

In addition to a variation in standards, there is also substantial confusion regarding low smoke zero halogen cables and the materials involved. Part of the confusion surrounds the product itself, variations as to what LSZH means and the fact that although cable suppliers are likely attempting to offer the best product possible, self-certification and testing can be counterproductive. The standards themselves have led to confusion. Here is a recap ranging from earlier standards to the latest, for example, and it is apparent as to why variations in halogen content exist:

IEC -1—Test on gases evolved during combustion of materials from cables—Part 1: Determination of the halogen acid gas content

IEC -2—Test on gases evolved during combustion of materials from cables—Part 2: Determination of acidity (by pH measurement) and conductivity

The above standards fail to consider chlorine, bromine or fluorine content and use the titration and pH and conductivity methods, respectively, to test halogen content. IEC -2 describes recommended pH value performance values rather than mandating them.

In , the IEC developed the LSHF -1, -2 and -3 standard series, Electric Cables—Halogen Free, Low Smoke, Thermoplastic-Insulated and Sheathed Cables of Rated Voltages up to and including 450/750 V.

This standard prompted the UL to create two certification programs, a material recognition service that employs test methods from IEC -1/-2 and IEC -1/-2 under Subject Outline UL , Outline of Investigation for Acid Gas, Acidity and Conductivity of Combusted Material and Assessment of Halogens. Cables certified under UL’s Recognized Component program are published in UL’s Online Certifications Directory so that cable manufacturers globally can search for compliant halogen-free wire and cable materials.

UL created Halogen Free (HF) and Low Smoke Halogen Free (LSHF) optional certification marks for wire and cable, and the requisite testing to ensure compliance to the IEC series of standards covering such categories as communications cable, optical fiber, flexible cords, power and control tray cable (TC), and appliance wiring material (AWM). The markings indicate that the cable automatically meets other UL general certification requirements, and certifications are covered under UL’s Follow-Up Service (FUS) program for monitoring and testing.

There are additional standards that are not as comprehensive as the above-mentioned ones, only covering cable jackets, for example, rather than the complete cable construction.

Virtually all European installations are mandated to meet the latest IEC specification. In addition, there is high demand that new installations also meet IEC -3, representing a more stringent LSZH flammability specification.

Additional tests over and above those carried out on PVC/LSF variants include:

• EN -2-1, which stipulates that emissions of hydrochloric acid must not exceed 0.5%, and
• EN -2 that stipulates that during the burning process visibility must not be reduced by more than 40%.

BS EN -1 establishes testing covering permissible levels of acidity, conductivity and fluorine produced through the burning process for LSZH flexible cable.

In an Actual Fire

In a fire situation, many synthetic materials will burn. In most fires, PVC is only one of the culprits. In several documented cases involving the presence of PVC, however, the fires would not have occurred, spread rapidly or emitted gases and chemicals that were life threatening if PVC were not present.

There are four elements involved with the burning of PVC, including hydrochloric acid in the smoke, dioxin, the spread of the fire, and wire and cable insulation. When PVC is involved, the fatalities are due to smoke inhalation. Today, that means hydrochloric acid in the smoke, while in the past, when substantially less synthetics are used in the environment (including wire and cable), it would have meant carbon monoxide in the smoke. These synthetics include not only PVC, but also vinyl in tile, plastic in furniture and carpeting, etc. The tragedy, unfortunately, is that the environment rapidly becomes a virtual gas chamber, often in just a couple of minutes.

Summary

Halogens produce toxic and corrosive combustion byproducts. While on one hand they are flame retardant in nature, they emit toxic gases when burned and damage electronics. PVC will remain a viable solution for wire and cable well into the future, because of its versatile performance and cost effectiveness. In closed environments, however, LSZH continues to gain in popularity. Not only is it substantially safer to use where humans are working or living, compound formulation continues to dramatically improve LSZH, and standards now exist to ensure the product is compliant to today’s stringent testing and chemical requirements.

As the use of LSZH climbs, it is important to establish that what is being purchased is actually LSZH. The availability of testing and criteria established by the UL was needed to spur transition, moving from supplier self-certification to an important standard and clear and verifiable criteria. Still, there is substantial material on the market today that claims to be low-smoke but actually is not.

Quabbin Wire & Cable, for example, has an LSZH product available now that meets the flame and low smoke requirements and complies with IEC and IEC , but haven’t completed certification yet. Expectations are that a move toward LSZH will continue to gain traction as suppliers become UL compliant and its cost continues to decline.

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