As critical components for power transmission and signal communication, the combustion performance of wires and cables directly impacts safety during fire incidents. These products are ubiquitous in various buildings, transportation vehicles, and industrial facilities. In the event of a fire, their burning rate, smoke emission, and toxic byproducts significantly affect evacuation and rescue efficiency, even posing life-threatening risks. Therefore, conducting scientific and systematic combustion performance testing on wires and cables is of utmost importance.

Through professional flammability tests, key parameters such as fire resistance, burning speed, and smoke production can be scientifically evaluated when wires and cables are exposed to flames. This allows for the selection of products with superior flame-retardant properties, which is crucial for enhancing electrical safety standards in construction and ensuring fire safety.

Why Fire Testing for Wires & Cables is Essential

✔ Prevent Rapid Fire Spread – Flame-retardant cables slow down combustion, allowing more time for evacuation.

✔ Reduce Toxic Smoke – Low-smoke, zero-halogen (LSZH) cables minimize hazardous gas emissions.

✔ Meet Regulatory Compliance – Mandatory in construction, railways, ships, and data centers.

✔ Enhance Public Safety – Critical for hospitals, airports, and high-rise buildings.

Evaluation Standards for Fire Performance of Electric Cables and Wires in Different Regulatory Systems.

The fire performance of electric cables and wires is assessed according to distinct standards under various national regulations.

European System (Construction Products Regulation - CPR)

In Europe, the Construction Products Regulation (CPR) mandates that all electric cables installed in buildings must undergo rigorous fire performance testing. The evaluation is based on EN 13501-6, which classifies cables according to their reaction to fire. The testing methods include:

ISO 1716 – Determination of the gross heat of combustion (calorific value)

EN 50399 – Flame spread and heat release rate under fire conditions

IEC 60332-1-2 – Flame propagation for single vertical insulated wires/cables

IEC 61034-2 – Measurement of smoke density under defined conditions

IEC 60754-2 – Determination of halogen acid gas emission

This comprehensive approach ensures that cables used in European construction meet stringent safety requirements for flame spread, smoke production, and toxicity.

U.S. System (Underwriters Laboratories - UL & NFPA Standards)

In the United States, fire-rated cables must comply with UL (Underwriters Laboratories) and NFPA (National Fire Protection Association) standards. Cables that pass the required tests are marked with a UL identification, fire rating, and approval number. Key test methods include:

UL 910 / NFPA 262 – Flame and smoke testing for plenum cables (air-handling spaces)

UL 1666 – Flame propagation testing for riser cables (vertical shaft applications)

UL 1581 – General flammability testing for wires and cables

UL 1685 – Vertical-tray fire-propagation and smoke-release test

These standards ensure that cables used in different U.S. applications (e.g., plenum, riser, general-purpose) exhibit appropriate fire resistance and low smoke emission.

The fire performance testing of electric cables and wires is crucial for evaluating their flame retardancy, smoke emission, toxicity, and flame spread characteristics under fire conditions. Although different countries and regions adopt varying standard systems, the core testing methods mainly include the following categories:

1. Flame Spread Tests:

(1) ZL-1028 Single Vertical Flame Test Chamber (IEC 60332-1 / GB/T 18380.1)

Applicable Standards: IEC 60332-1, UL 1581 VW-1, GB/T 18380.1

Testing Method:
 

A single cable is vertically fixed and exposed to a standard flame (20/30/45 seconds).

Flame spread height and self-extinguishing time are observed.

Application: Evaluates the flame retardancy of a single cable.

(2) ZL-1048 Bundle Vertical Flame Test Machine (IEC 60332-3 / GB/T 18380.3)

Applicable Standards: IEC 60332-3, UL 1685, GB/T 18380.3

Testing Method:

Multiple cables are vertically installed in a bundle and exposed to high-intensity flames (20.5 kW, 40 minutes).

Flame spread height and charring length are measured.

Application: Simulates fire behavior in densely installed cable scenarios.

(3) ZL-1021 Horizontal Flame Test Machine (UL 1581 FT1/FT2/FT4)

Applicable Standards: UL 1581 (FT1/FT2/FT4), IEC 60332-2

Testing Method:

Cables are placed horizontally and exposed to a flame (30 seconds).

Burning distance and self-extinguishing time are observed.

Application: Assesses flame retardancy of low-smoke zero-halogen (LSZH) cables.

Smoke Density Tests:

(1) ZL-1049 Smoke Density Test Chamber (IEC 61034 / GB/T 17651)

Applicable Standards: IEC 61034, GB/T 17651, ASTM E662

Testing Method:

Cables are burned in a sealed chamber, and light transmittance is measured.

Specific optical density (smoke concentration) is calculated.

Application: Evaluates the impact of smoke on visibility during a fire.

(2) NBS Smoke Chamber Test Machine (ASTM E662 / NFPA 258)

Applicable Standards: ASTM E662 (U.S.), NFPA 258

Testing Method:

Samples are burned under controlled conditions, and smoke optical density (Ds value) is measured.

Application: Used in the U.S. market to assess smoke obscuration.

3.Toxicity Tests:

(1)ZL-1050 Halogen Acid Gas Emission Test Machine(IEC 60754 / GB/T 17650)

Applicable Standards: IEC 60754, GB/T 17650

Testing Method:

Cables are burned, and halogen acid gases (HCl, HBr, etc.) are collected.

pH value and conductivity are calculated.

Application: Assesses the environmental safety of LSZH cables.

4.Oxygen Index Test:

(1) ZL-3010 Limiting Oxygen Index (LOI) Test Machine (ISO 4589 / ASTM D2863)

Applicable Standards: ISO 4589, ASTM D2863, GB/T 2406

Testing Method:

Measures the minimum oxygen concentration required to sustain combustion in a nitrogen-oxygen mixture.

Materials with LOI > 28% are considered flame-retardant.

Application: Determines the flame-retardant grade of cable materials.

5.Heat Release & Fire Propagation Tests:

(1) Cone Calorimeter Test Machine (ISO 5660 / ASTM E1354)

Applicable Standards: ISO 5660, ASTM E1354

Testing Method:

Simulates real fire conditions to measure heat release rate (HRR) and total heat release (THR).

Application: Assesses fire growth rate.

(2) Cable Tray Fire Test Machine (EN 50266 / UL 1685)

Applicable Standards: EN 50266 (Europe), UL 1685 (U.S.)

Testing Method:

A bundle of cables is burned in a simulated cable tray, and flame spread distance is measured.

Application: Evaluates fire risks in large-scale cable installations.

Fire testing of electric cables and wires not only plays a crucial role in evaluating and improving the safety performance of cable products, but also holds profound value and significance in formulating safety standards, fire safety management, and raising public safety awareness. Therefore, strengthening research and application of cable fire testing is of great practical importance for ensuring public safety and promoting the sustainable development of the cable industry.