IEC 60331 Fire Resistant Cable: What the Standard Actually Requires

IEC 60331 is the international standard that determines whether a cable can maintain circuit integrity during a fire. If you are specifying fire resistant cables for emergency circuits — fire alarms, emergency lighting, smoke extraction fans, sprinkler pumps, elevator recall — IEC 60331 is the standard your cables must pass.

But IEC 60331 is not a single test. It is a family of standards with multiple sub-parts, each covering different cable types, voltage ratings, and test conditions. Specifying "IEC 60331 compliant" without understanding which sub-part applies to your cable leads to procurement errors, failed inspections, and project delays.

This guide breaks down every sub-part of IEC 60331, explains exactly what happens during testing, what constitutes a pass or fail, and how to write a cable specification that ensures you receive genuinely fire resistant cables — not just cables with a certificate.

What IEC 60331 Measures — Circuit Integrity Under Fire

IEC 60331 answers one question: Can this cable continue to carry current while it is burning?

This is fundamentally different from IEC 60332 (flame retardancy), which only asks whether fire spreads along a cable. A cable can pass IEC 60332 (fire does not propagate) but completely fail IEC 60331 (circuit fails within minutes of fire exposure).

The Critical Distinction

• IEC 60332 (Flame Retardant): Cable self-extinguishes when fire source is removed. Circuit is destroyed — cable no longer functions. Purpose: prevent fire spread.
• IEC 60331 (Fire Resistant): Cable maintains electrical function throughout the fire. Circuit continues working while burning. Purpose: maintain life-safety circuits during evacuation.

This means every IEC 60331 cable must also inherently possess construction features that prevent short-circuit between conductors at extreme temperatures — the insulation cannot simply melt away or it would short-circuit and fail the test.

IEC 60331 Sub-Parts Explained

The standard is divided into sub-parts that cover different applications. The current structure (post-2009 consolidation) groups test methods into IEC 60331-1 and IEC 60331-2, which differ by cable diameter — both include fire and mechanical shock:

Current Test Method Standards

Note: IEC 60331-1 states that by agreement between manufacturer and purchaser, the test procedure may also be used for cables rated up to 3.3 kV with suitable fuses.

Legacy Sub-Parts (Consolidated into IEC 60331-1/2)

The following sub-parts existed under the 1999 edition of the standard. They have since been withdrawn, with their content consolidated into IEC 60331-1 and IEC 60331-2. You will still see these referenced in existing certificates, specifications, and building codes:

Cables tested to IEC 60331-21 or IEC 60331-23 under the previous framework remain valid — the test methodology is unchanged, only the document structure was consolidated.

Which Sub-Part Do You Need?

For most building projects:

• Power cables with overall diameter >20 mm (large multi-core, armoured): IEC 60331-1
• Smaller cables ≤20 mm diameter (fire alarm, emergency lighting, control cables): IEC 60331-2
• Cables rated above 0.6/1kV (up to 3.3 kV): IEC 60331-1 by agreement between manufacturer and purchaser

Both IEC 60331-1 and IEC 60331-2 include mechanical shock as part of the test — there is no current IEC 60331 sub-part that tests fire resistance without shock. This reflects the reality that falling debris accompanies real building fires.

The IEC 60331 Test Procedure — Step by Step

Understanding the test procedure helps you evaluate whether a supplier's test certificate is meaningful or just paper.

Test Setup

1. Cable sample length: Minimum 1200 mm of cable mounted horizontally on a steel ladder support
2. Electrical circuit: Cable is energized at its rated voltage throughout the test. A monitoring device continuously checks for circuit failure (short-circuit between conductors, or open-circuit due to conductor break)
3. Burner: A ribbon-type propane burner providing uniform flame across a 600 mm length of the cable
4. Temperature monitoring: Thermocouples positioned on the cable surface confirm the required temperature is maintained throughout the test duration

Test Execution (IEC 60331-1 and IEC 60331-2 — Both Include Mechanical Shock)

1. Cable is energized at rated voltage with monitoring circuit active
2. Burner is ignited — cable surface temperature must reach 830°C ± 40°C within the first 5 minutes
3. Temperature is maintained at 830°C ± 40°C for the specified duration (minimum 90 minutes for most requirements)
4. During the fire exposure, a mechanical shock device strikes the cable at specified intervals — simulating debris impact during a real fire
5. Throughout the entire test, the monitoring circuit checks for any interruption or short-circuit

The difference between IEC 60331-1 and IEC 60331-2 is not the test severity — it is the test apparatus size. IEC 60331-1 uses apparatus designed for larger cables (>20 mm OD), while IEC 60331-2 uses apparatus scaled for smaller cables (≤20 mm OD). The fire temperature, duration, and shock requirements are the same.

Pass Criteria

The cable passes IEC 60331 if:

• The circuit remains intact for the entire specified duration (typically 90 or 120 minutes)
• No short-circuit occurs between any conductors
• No open-circuit occurs (conductor does not break)
• The cable continues to carry its test current without interruption

The cable fails if at any point during the test:

• The monitoring circuit detects a break (open-circuit) lasting more than 2 seconds
• A short-circuit occurs between any two conductors
• A short-circuit occurs between any conductor and the metallic sheath or armour

What This Means for Buyers

A cable that passes IEC 60331 at 830°C for 90 minutes will maintain circuit function in any standard building fire (ISO 834 fire curve reaches approximately 1000°C only after several hours). This provides the safety margin required for evacuation and firefighting operations.

Cable Construction That Passes IEC 60331

Not every cable construction can pass IEC 60331. The standard does not specify construction — it only specifies performance. But decades of testing have established which constructions reliably pass:

1. Mica Tape + XLPE/EPR Insulation (Most Common)

Construction: Copper conductor → mica glass tape wrap (1-2 layers) → XLPE or EPR primary insulation → bedding → armour (optional) → LSZH or PVC outer sheath

How it works: When fire destroys the XLPE/EPR insulation, the mica tape layer remains intact. Mica (a natural mineral silicate) has a decomposition temperature above 900°C and maintains its dielectric properties throughout the fire test. The mica tape becomes the sole insulation barrier between conductors.

Typical designations:

• NH-YJV (China, GB/T 19666)
• WDZN-YJY (China, low smoke zero halogen + fire resistant)
• N2XH-FE180 (Germany/IEC, E30/E60/E90 rated)
• NHXH-FE180/E90 (IEC, halogen-free fire resistant)

2. Mineral Insulated (BTTZ/MICC) — Highest Performance

Construction: Copper conductor → compressed MgO powder → seamless copper sheath

How it works: No organic material exists to burn. The cable cannot fail IEC 60331 because nothing degrades at fire temperatures. MgO melting point (2,852°C) far exceeds any building fire.

Limitation: Rigid construction, specialized termination, higher cost. Covered in detail in our BTTZ Mineral Insulated Cable Guide.

3. Silicone Rubber + Mica Tape

Construction: Copper conductor → mica tape → silicone rubber insulation → glass braid or mica barrier → silicone or LSZH sheath

How it works: Silicone rubber, when burned, forms a rigid ceramic-like ash (silicon dioxide) that provides additional mechanical protection to the mica layer. This construction offers better flexibility than standard mica-tape XLPE cables.

What Construction NOT to Specify

• PVC-insulated cables cannot pass IEC 60331 — PVC decomposes at 200-300°C and becomes conductive
• XLPE-only cables (without mica tape) cannot pass — XLPE melts at approximately 120°C and burns away completely
• Cables marketed as "fire rated" without mica tape or mineral insulation — if the manufacturer cannot explain the fire-barrier mechanism, the cable will not pass IEC 60331

IEC 60331 vs Related Standards — Know the Differences

Engineers and procurement teams frequently confuse these standards. Here is the definitive comparison:

IEC 60331 vs IEC 60332

IEC 60331 vs BS 6387

IEC 60331 vs EN 50200

For international procurement: IEC 60331 is the safest specification. It is recognized worldwide, and any cable tested to IEC 60331 can also typically demonstrate compliance with regional equivalents.

How to Specify IEC 60331 Cables — Avoid These Common Mistakes

Writing the Specification Correctly

A properly written fire resistant cable specification must include:

1. Which sub-part: "Cable shall comply with IEC 60331-1" or "IEC 60331-2" (not just "IEC 60331")
2. Duration: "Circuit integrity maintained for minimum 120 minutes" (90 min is standard minimum, but many projects require 120 min)
3. Cable diameter context: IEC 60331-1 covers cables with OD >20 mm; IEC 60331-2 covers OD ≤20 mm — specify accordingly
4. Voltage rating: "Rated 0.6/1kV" (for higher voltages up to 3.3 kV, IEC 60331-1 applies by agreement)
5. Sheath type: LSZH required for indoor installations in most modern codes
6. Armour requirement: SWA or non-armoured, depending on mechanical protection needs

Example specification line:

"All fire alarm loop cables shall be 2-core 1.5mm² Cu/Mica/XLPE/LSZH, compliant with IEC 60331-2 (circuit integrity with fire and mechanical shock, 830°C for 120 minutes, cable OD ≤20 mm). Test certificate from accredited laboratory (ILAC/MRA recognized) required with submission."

"Main fire pump supply cable shall be 4-core 35mm² Cu/Mica/XLPE/SWA/LSZH, compliant with IEC 60331-1 (circuit integrity with fire and mechanical shock, 830°C for 120 minutes, cable OD >20 mm). Test certificate from accredited laboratory required."

Common Specification Mistakes

Mistake 1: Writing "IEC 60331 compliant" without specifying sub-part

This leaves ambiguity about which test apparatus was used. IEC 60331-1 and IEC 60331-2 have different apparatus sizes matched to different cable diameters. Always specify the correct sub-part for your cable size.

Mistake 2: Not requiring an accredited test certificate

Many manufacturers provide "self-declared" conformity or test certificates from non-accredited laboratories. Insist on:

• Test conducted by laboratory accredited under ISO 17025
• Laboratory is ILAC/MRA signatory member
• Certificate references the specific cable construction (not just the manufacturer's range)
• Sample tested matches the exact cross-section and core count you are purchasing

Mistake 3: Confusing fire resistance with enhanced fire resistance

Some projects require fire resistance beyond IEC 60331 minimum. For example:

• Standard IEC 60331: 830°C for 90 minutes
• Enhanced: 830°C for 120 minutes
• BS 6387 CWZ: 950°C with water AND mechanical shock (most severe)

If your fire engineer specifies "enhanced fire resistance," clarify the exact temperature, duration, and whether water/shock tests are needed.

Mistake 4: Accepting IEC 60332 certificates as proof of fire resistance

This happens more often than you would expect. IEC 60332 (flame retardant) is NOT IEC 60331 (fire resistant). A cable passing IEC 60332-1 only means fire does not spread — it says nothing about circuit integrity during fire. Every fire resistant cable also passes IEC 60332, but NOT every flame retardant cable passes IEC 60331.

Fire Duration Requirements by Application

Different circuits require different fire endurance durations. These are typically set by the fire engineer or local building code:

Important: These durations are for the cable fire resistance rating. The total system survival time also depends on:

• Cable route (does it pass through the fire zone?)
• Mounting method (cables on open ladder have less protection than cables in fire-rated conduit)
• Fire compartmentation (fire may not reach the cable if compartment barriers hold)

Regional Standard Equivalents — Cross-Reference Table

If your project specification references a regional standard, here is how it maps to IEC 60331:

For export/international projects: Specifying IEC 60331 ensures worldwide recognition. If a regional code requires a local standard, ask the cable supplier to provide cross-reference documentation showing IEC 60331 equivalence.

Verifying IEC 60331 Compliance — What to Check Before Purchase

Step 1: Request the Type Test Report

A genuine IEC 60331 type test report should contain:

• Test laboratory name and accreditation number
• Date of testing
• Cable construction details (conductor size, insulation type, number of cores, outer diameter)
• Test conditions (temperature achieved, duration, whether mechanical shock was applied)
• Monitoring circuit details (voltage applied, how continuity was monitored)
• Result: PASS with duration achieved (must equal or exceed the specified requirement)

Step 2: Verify the Test Laboratory

• Check that the laboratory is ISO 17025 accredited
• Confirm the accreditation scope includes fire testing of cables
• For high-value contracts, verify directly with the laboratory that the certificate is genuine (fraudulent certificates exist in the market)

Step 3: Match Certificate to Product

The test certificate applies ONLY to the exact cable construction tested. Changes in:

• Mica tape brand or type
• Number of mica tape layers
• Conductor size (a 4mm² test does not cover 16mm²)
• Number of cores (a 2-core test does not cover 4-core)
• Sheath material

...may require separate testing. Ask the supplier: "Does your type test cover the exact cable size and core count I am ordering?"

Step 4: Factory Audit (For Large Orders)

For projects exceeding $50,000 in fire resistant cable value, consider:

• Verifying mica tape inventory matches the brand on the type test
• Checking that mica tape wrapping equipment applies consistent tension and overlap
• Reviewing production quality control records for fire resistant cable batches
• Requesting routine test samples from your production batch for independent verification

Why Specification Matters — Real Project Consequences

Incorrectly specified or counterfeit fire resistant cables create genuine life-safety risks:

During fire events:

• Circuits fail within minutes instead of maintaining 90+ minute integrity
• Emergency lighting goes dark during evacuation
• Sprinkler pumps lose power — fire suppression fails
• Fire alarm system goes silent — occupants in remote areas do not evacuate

During inspections:

• Fire authority rejects installation — cables must be ripped out and replaced
• Project completion delayed by months while replacement cables are manufactured and shipped
• Contractor faces liability for installing non-compliant materials
• Insurance implications for building owner if fire rating is compromised

The cost difference between a genuine IEC 60331 cable and a non-compliant cable is typically 15-30% per meter. The cost of replacing installed cable is 10-50× the material cost (demolition, re-routing, re-testing, project delay, lost occupancy revenue).

Source IEC 60331 Fire Resistant Cables — Factory Direct

We manufacture fire resistant cables tested and certified to IEC 60331-1 (with mechanical shock) in our dedicated fire cable production facility. Our mica tape wrapping lines maintain consistent tape tension and overlap ratio — the two most critical quality factors for fire resistance performance.

Available constructions:

• Cu/Mica/XLPE/SWA/LSZH (armoured, low smoke zero halogen)
• Cu/Mica/XLPE/LSZH (non-armoured, indoor use)
• Cu/Mica/EPR/LSZH (enhanced flexibility for complex routing)
• Multi-core control cables: 2-core to 37-core, 1.5mm² to 6mm²
• Power cables: 1-core to 5-core, 1.5mm² to 400mm²

Certifications held:

• IEC 60331-1 type test (830°C, 90 minutes with mechanical shock)
• IEC 60332-1 single cable flame test
• IEC 60332-3 Category A bundled cable flame test
• IEC 61034 smoke density test
• IEC 60754 halogen acid gas emission test (for LSZH cables)

What to include in your inquiry:

• Cable schedule: type designation, core count × cross-section, quantity in meters
• Fire resistance duration required (90 min or 120 min)
• Which IEC 60331 sub-part applies: IEC 60331-1 (cable OD >20 mm) or IEC 60331-2 (cable OD ≤20 mm)
• Sheath requirement: LSZH or PVC
• Armour requirement: SWA, non-armoured, or both
• Destination country and applicable local standard (for regional certification cross-reference)
• Required documentation: type test report, routine test certificate, material certificates

For detailed information on specific fire cable types in our range:

• Fire Resistant Cable Manufacturer Guide — Full Product Range
• BTTZ Mineral Insulated Cable — Unlimited Fire Duration
• LSZH Cable Specifications & Sizes

Frequently Asked Questions

What is the difference between IEC 60331-1 and IEC 60331-2?

Both standards test circuit integrity under fire with mechanical shock at 830°C. The difference is cable size: IEC 60331-1 applies to cables with an overall diameter exceeding 20 mm (typically multi-core power cables with armour), while IEC 60331-2 applies to cables with OD of 20 mm or less (typically fire alarm cables, small control cables, emergency lighting circuits). The test apparatus is scaled differently, but fire temperature, duration, and shock severity are the same.

Can a PVC cable pass IEC 60331?

No. PVC decomposes at 200-300°C and becomes electrically conductive when charred. It is physically impossible for PVC insulation alone to maintain circuit integrity at 830°C. A fire resistant cable must contain mica tape or mineral insulation as the fire barrier.

Does IEC 60331 guarantee the cable will work for exactly 90 minutes in a real fire?

The 90-minute rating is the minimum the cable demonstrated in a controlled laboratory test at 830°C. In a real fire, performance depends on actual fire temperature, cable loading, installation method, and whether the cable is mechanically damaged before the fire. The laboratory test provides a standardized benchmark — actual performance in a specific fire may be longer or shorter than the rated duration.

Is IEC 60331 the same as E90?

E90 is a European classification (per EN 13501-6) indicating 90 minutes of circuit integrity. It is based on testing per IEC 60331 methodology. So E90 = IEC 60331 tested for 90 minutes. Similarly, E30 = 30 minutes, E60 = 60 minutes, E120 = 120 minutes.

How do I know if a Chinese manufacturer's IEC 60331 certificate is genuine?

Check three things: (1) the test laboratory is ISO 17025 accredited and appears in the ILAC database, (2) the certificate number can be verified directly with the laboratory, (3) the cable construction on the certificate exactly matches what you are purchasing. For additional confidence, request that the manufacturer send a sample to an independent laboratory for verification testing before placing a large order.

What is GB/T 19216 and how does it relate to IEC 60331?

GB/T 19216 is the Chinese national standard for fire resistant cable testing. It is a direct adoption of IEC 60331 — the test procedures, apparatus, and pass/fail criteria are identical. A cable passing GB/T 19216 is technically equivalent to passing IEC 60331. However, for international projects, request testing specifically referenced to IEC 60331 for clearer recognition by consultants and authorities.

Should I specify IEC 60331 or BS 6387 for my project?

If your project follows IEC-based codes (most of the world), specify IEC 60331. If your project is in the UK, UAE, Qatar, or follows British standards, BS 6387 CWZ is often required and is actually more demanding than IEC 60331 (higher temperature: 950°C vs 830°C, plus water spray test). Some Middle East projects accept either standard — confirm with the fire consultant.