IEC 60332-3-25:2018

Overview

IEC 60332-3-25:2018 is an international test standard for assessing vertical flame spread on vertically mounted bunched wires or cables - electrical or optical - under controlled fire conditions. Designated Category D, it is intended specifically for small cables (overall diameter ≤ 12 mm; conductor cross-section ≤ 35 mm²) assembled in a touching formation on the front of the standard test ladder with a nominal non‑metallic material volume of 0.5 l/m. The flame is applied for 20 minutes using the apparatus specified in IEC 60332-3-10 and the flame source is a ribbon‑type propane burner. The test is primarily for type approval and to demonstrate a cable’s ability to limit flame spread.

Key technical topics and requirements

• Scope: Vertical flame spread assessment of bunched small cables (electrical or optical) in a touching configuration.
• Test sample: Multiple pieces from the same production length, each ≥ 3.5 m; number chosen to reach 0.5 l/m non‑metallic material.
• Cable limits: Overall diameter ≤ 12 mm; conductor cross‑section ≤ 35 mm² (or optical fibre cables).
• Mounting: Front side of the standard ladder in touching formation only (arrays of cables in contact).
• Ignition & apparatus: Ribbon‑type propane gas burner per IEC 60332-3-10.
• Test duration: 20 minutes flame application.
• Evaluation: Flame spread quantified by the extent of damage (char/consumption) of the test sample.
• Guidance and performance: Cable selection guidance in Annex A; recommended performance criteria in Annex B.
• Edition note: Edition 2.0 (2018) is a technical revision that added Category D to the IEC 60332-3 series.

Practical applications and users

Who uses IEC 60332-3-25:

• Cable manufacturers performing type approval and product development for communication and power small-diameter cables.
• Test laboratories conducting standardized vertical flame spread evaluations for compliance and reporting.
• Specifiers, designers and safety engineers assessing fire performance of cable installations in buildings, transport, and industrial systems where very low volumes of non‑metallic cable materials are used.
• Regulatory and certification bodies referencing IEC flame‑spread data for procurement and rules.

Practical value:

• Provides a repeatable method to compare flame‑spread behavior of small cable designs.
• Helps manufacturers minimize combustible material or validate construction choices (jackets, fillers, optical sheaths) to meet safety expectations.
• Supports documentation for safety dossiers, tender responses, and product certification.

Related standards

• IEC 60332-3-10 (apparatus for vertical flame spread tests)
• Other parts of the IEC 60332-3 series (Parts 3-21 to 3-24 for Categories A–C)
• IEC 60695-4 and IEC 60811 series (terminology and material test methods)
• IEC Guide 104 (group safety publication status)

Keywords: IEC 60332-3-25, vertical flame spread, Category D, small cables, cable fire test, type approval, IEC 60332 series.