IEC 60332-3-23:2018

Overview - IEC 60332-3-23:2018 (Category B)

IEC 60332-3-23:2018 is an international test method for assessing vertical flame spread of vertically-mounted bunched electric and optical fibre cables (Category B). Intended primarily for type approval testing, the standard defines how to mount a bundle of cables on the standard ladder, the test duration, and the measurement of flame spread to determine a cable’s ability to limit vertical propagation of fire under defined conditions.

Key measurable parameters from the standard:

• Nominal total volume of non-metallic material: 3.5 l/m of test sample
• Flame application time: 40 minutes
• Mounting: front of the standard ladder (with improved mounting details in Edition 2)
• Measurement: flame spread assessed as the extent of damage/char to the cable sample

This edition clarifies applicability to optical fibre cables (in addition to metallic conductor cables) and refines mounting procedures to improve repeatability and reproducibility.

Key topics and technical requirements

• Test configuration: cables are bunched vertically on the standard ladder to achieve the specified 3.5 l/m non‑metallic volume.
• Mounting rules: the standard specifies whether cables are spaced or touching depending on conductor size:
  • Cables with at least one conductor > 35 mm² are mounted spaced.
  • Cables with conductors ≤ 35 mm² and optical fibre cables are mounted touching.
• Ignition source and apparatus: uses the apparatus described in IEC 60332-3-10 and a ribbon‑type propane burner as the ignition source.
• Evaluation: flame spread is quantified by the damaged extent of the cable sample; Annex B provides a recommended performance requirement.
• Selection: Annex A gives guidance on selecting representative cables for type approval testing.
• Status: published as a group safety publication in accordance with IEC Guide 104.

Practical applications and users

Who uses IEC 60332-3-23:

• Cable manufacturers performing type approval and product development.
• Accredited fire test laboratories conducting vertical flame spread tests on bunched cable installations.
• Fire safety engineers and specifiers assessing cable fire performance for buildings, infrastructure, and industrial installations.
• Regulators and procurement teams specifying minimum fire performance criteria for installed cable systems.

Practical uses:

• Demonstrating a cable’s ability to limit flame spread in vertical bundles.
• Comparing cable constructions (insulation, sheathing, fibre vs metallic) under standardized test conditions.
• Supplying test evidence for compliance, certification, or product selection.

Related standards

• IEC 60332-3-10 - Apparatus for vertical flame spread tests
• IEC 60332-3-21 / 3-22 / 3-24 / 3-25 - Other Category methods (A, C, D, etc.)
• IEC 60695-4 - Fire hazard terminology
• IEC Guide 104 - Preparation and use of safety publications

Keywords: IEC 60332-3-23, vertical flame spread, Category B, cable fire test, optical fibre cable, test ladder, 3.5 l/m, 40 min, type approval.