Fire resistant test standards – explained!

In our previous Keystone Academy blog ‘What is the Difference Between FRT and FR Cable?’, we shared that Fire Resistant (FR) cables are a fire safety product, which means they not only reduce the spread of fire, but will also maintain circuit integrity in the presence of fire.

FR FRT Standards
This is critical so that life-saving electrical installations such as fire alarms, smoke detectors, PA systems, and emergency lighting, are able to perform their functions in the event of a fire.

In addition to complying with LSZH flame retardant (FRT) tests (IEC 60332, IEC 60754, and IEC 61034), LSZH FR cables are also tested to IEC 60331-21, BS 6387 or SS 299-1 to ensure that the fire-resistant cables maintain circuit integrity under fire conditions. In this article, we introduce the differences among the 3 common LSZH FR test standards.


Resistance to Fire: IEC 60331-21

IEC 60331-21 is the basic international testing standard for fire resistant cables. There is one set of requirements to test for cable’s circuit integrity under fire:

• Resistance to fire alone (Temperature of at least 750°C for 90 mins)

This test standard is suitable for low voltage power cables and control cables with a rated voltage up to and including 0.6/1kV. During the test, the cable is connected to a transformer output with a 2A fuse in each phase. The test is deemed successful if there are no fuse fails and the test light is not extinguished.


Resistance to Fire: SS 299-1

Singapore Standard SS 299-1:1998 specifies tests for fire resistant cables, with different category symbols assigned depending on the test parameters. 

• Resistance to fire alone (Category A, B, C, or S)

Fire Alone-1

Optional: Resistance to fire with water (Category W)
 This is meant to simulate fire in the presence of activated sprinkler systems.

Fire with water-1

• Optional: Resistance to fire with mechanical shock (Category X, Y, or Z)
This is meant to simulate fire in the presence of disturbances such as falling debris.

Fire with mechnical shock-1
*Note: Cat. CWZ would be equivalent to the BS 6387:2013 standard requirement

The first symbol will be based on resistance to fire alone, and only where there are other optional tests applied, then it would be followed by one or more other symbols. For instance, if you come across a fire resistant cable that indicates it fulfills SS299-1 Cat. CY, it would mean that this cable has passed the following tests:

• Resistance to fire alone, Category C (950 °C ±40 °C for 3 hours)
• Resistance to fire with mechanical shock, Category Y (750 °C ±40 °C 15 mins flame, mechanical shock every 30s)

Resistance to Fire: BS 6387

British Standards BS 6387 is the most commonly recognised FR cable test standard.
Based on the latest standards update BS6387:2013, an FR cable is considered compliant only if it passes the BS 6387 Cat. CWZ requirement:

• Resistance to fire alone, Category C (950 °C ±40 °C for 3 hours)
• Resistance to fire with water, Category W (650 °C ±40 °C 15 mins flame, 15 mins water)
• Resistance to fire with mechanical shock, Category Z (950 °C ±40 °C 15 mins flame, mechanical shock every 30s)

Keystone Cable’s fire resistant range complies with all of the above international standards.