| Full title | Common test methods for cables under fire conditions. Heat release and smoke production measurement on cables during flame spread test. Test apparatus, procedures, results |
| Publisher | CENELEC (CLC/TC 20); published in the UK by BSI as BS EN 50399 |
| Current edition | EN 50399:2022. BS EN 50399:2022 published 31 October 2022 |
| Status | Current. Supersedes EN 50399:2011 and EN 50399:2011/A1:2016. Conflicting national standards withdrawn by 8 August 2025 |
| Related standards | EN 13501-6, EN 50575, EN 60332-1-2, EN IEC 60332-3-10, EN 61034-2 |
What it covers
EN 50399 specifies the apparatus and method for testing vertically mounted cables in a large-scale fire test. It measures vertical flame spread, heat release, smoke production and flaming droplets or particles.
It applies to power, control and communication cables, including optical fibre and hybrid cables. The test procedures are for type approval classification in CPR reaction to fire classes B1ca, B2ca, Cca and Dca. The cable installation on the ladder and the air flow through the chamber follow Commission Decision 2006/751/EC.
The test set-up
| Item | Requirement |
|---|---|
| Test chamber | Vertical chamber about 4 m high and 1 m wide, with a hood and exhaust duct above it |
| Ladder | Tubular steel ladder standing vertically in the chamber |
| Test pieces | Cable lengths of 3.5 m fixed to the front of the ladder |
| Ignition source | Propane ribbon burner in front of the cables, fed by mass flow controllers |
| Burner output | 20.5 kW or 30 kW, depending on the class being tested |
| Flame application | 20 minutes (1200 s) |
| Air flow through the chamber | 8000 l/min |
| Instrumentation | Oxygen and carbon dioxide analysers for heat release, and a light system (white light or laser) in the duct for smoke |
The number of cable lengths depends on the cable diameter, so that a defined width of ladder is covered.
Mounting by cable size
| Circular cable diameter | Mounting |
|---|---|
| ≥ 20.0 mm | Single lengths, spaced apart |
| > 5.0 mm and < 20.0 mm | Single lengths, spaced apart |
| ≤ 5.0 mm | Grouped into bundles, with the bundles spaced apart |
The 2022 edition adds provisions for testing flat cables, and gives mounting rules for circular and non-circular cables, including “figure of 8” cables. For class B1ca tests, a non-combustible board is fitted behind the cables.
What is measured
| Parameter | What it is |
|---|---|
| FS | Flame spread: the extent of damage up the cable after the test |
| HRR and peak HRR | Heat release rate, calculated from oxygen consumption, and its highest value |
| THR1200 | Total heat release over the 1200 s test |
| FIGRA | Fire growth rate index, derived from the heat release curve |
| SPR and peak SPR | Smoke production rate, from light obscuration in the exhaust duct, and its highest value |
| TSP1200 | Total smoke production over the 1200 s test |
| Flaming droplets | Observed occurrence of flaming droplets or particles, and how long they burn |
These results are compared with the limits in EN 13501-6 to set the main class and the smoke (s) and flaming droplets (d) classes.
Which classes use which burner
| Class | Flame source | Also needs |
|---|---|---|
| B1ca | 30 kW, with non-combustible backing board | EN 60332-1-2 |
| B2ca | 20.5 kW | EN 60332-1-2 |
| Cca | 20.5 kW | EN 60332-1-2 |
| Dca | 20.5 kW | EN 60332-1-2 |
Aca uses EN ISO 1716 instead. Eca and Fca use only EN 60332-1-2. The smoke class for B1ca must come from the 30 kW test, and for B2ca, Cca and Dca from the 20.5 kW test.
Changes in the 2022 edition
- The test apparatus is now described in full in EN 50399. The earlier edition referred to EN 60332-3-10 for it.
- Improvements to the chamber, burner, hood and duct, including mandatory mass flow controllers for the burner gases.
- New checks to qualify the equipment: a flame shape check and a performance check, with guidance in new informative Annexes K and L.
- New provisions for flat cables, covering mounting and the number of test pieces.
The date of withdrawal for conflicting national standards, including EN 50399:2011 and A1:2016, was 8 August 2025.
How it relates to other standards
- EN 13501-6 sets the class limits that EN 50399 results are judged against.
- EN 50575 is the CPR product standard for cables that calls up the classification.
- EN IEC 60332-3 series uses a similar vertical ladder and chamber but only measures charred height. It is not a CPR classification test.
- EN 50576 covers extended application of reaction to fire test results across a range of cable sizes.
What it means in practice
- A class of B1ca, B2ca, Cca or Dca must be backed by EN 50399 test results, either on the cable itself or extended to it under EN 50576. A cable with only an EN 60332-1-2 result can claim no better than Eca.
- A test report should state the edition of EN 50399, the flame source (20.5 kW or 30 kW) and the measured values, not only the class.
- The test rates the cable as tested in a standard mounting. Real installations with different bunching or containment can behave differently.
Related reading: What is LSZH cable and when do you need it?.