FIRE RESISTANT CABLES

This is a critical distinction for fire safety planning:

• Flame Retardant (e.g., IEC 60332): Designed to resist the spread of fire along the cable length. It self-extinguishes but will eventually lose electrical functionality if the core is burned.

• Fire Resistant (e.g., IEC 60331 / BS 6387): Designed to maintain circuit integrity and continue operating during a fire. These are mandatory for emergency lighting, fire alarms, and smoke extraction systems where power must stay on during an evacuation.

MICC is often considered the "ultimate" fire-resistant cable.

• Composition: It consists of copper conductors inside a copper sheath, insulated by compressed magnesium oxide powder.

• Pros: It is completely inorganic, meaning it cannot burn, produces zero smoke, and can operate at temperatures near the melting point of copper. It also acts as its own conduit.

• Cons: Higher material cost and requires specialized termination skills compared to polymeric cables.

Most polymeric fire-resistant cables utilize a Mica Tape wrap around the copper conductor.

• Function: Mica is a mineral that remains stable at extremely high temperatures. When the outer plastic insulation burns away, the Mica tape forms a hard, non-conductive "shell" that prevents short circuits between the conductors, allowing the cable to continue functioning.

Mainly used in British Standards (BS 6387), this is a "Gold Standard" test for fire cables:

• C: Resistance to fire alone ($950℃  for 3 hours).

• W: Resistance to fire and water (simulating sprinkler systems).

• Z: Resistance to fire and mechanical shock (simulating falling debris).

  A CWZ-rated cable ensures the highest level of survivability in a collapsing building environment.

In the international market, particularly for public infrastructure and high-rise buildings, PVC is often restricted.

• Safety: LSZH materials do not release corrosive "Acid Gas" (Hydrogen Chloride) when burned. This protects sensitive electronic equipment from corrosion and, more importantly, ensures that smoke is thin and non-toxic, allowing for clear visibility during emergency evacuations.

European standards classify cables by the duration they maintain integrity:

• Standard (PH30 / PH60): Tested to maintain the circuit for 30 or 60 minutes. Usually sufficient for general fire alarm systems in simple buildings.

• Enhanced (PH120): Tested for 120 minutes of continuous operation under fire and mechanical impact. These are required for large, complex buildings where evacuation times are longer.

Silicone Rubber is an alternative to Mica tape for fire resistance.

• Mechanism: When silicone burns, it leaves behind a non-conductive "ash" (silica) that maintains insulation.

• Application: These are highly flexible and easier to strip/terminate than Mica-wrapped cables, making them popular for flexible fire alarm wiring in restricted spaces.