OFNP, CMP, and LSZH Cable Types Explained in Structured Cabling

In modern structured cabling systems—especially in data centers, hospitals, airports, and high-rise buildings—fire safety and environmental performance are just as important as transmission performance. Three commonly referenced cable standards are OFNP, CMP, and LSZH. Although they are often mentioned together, they actually belong to different classification systems.

This article explains what they mean and how they differ.

1. CMP (Communications Plenum Cable)

Underwriters Laboratories defines CMP (Communications Plenum) as the highest fire-resistance rating for copper communication cables in UL standards.

Key Features:

High flame resistance
Very low smoke generation
Suitable for plenum spaces (air circulation areas)

Typical Applications:

Air handling spaces above ceilings
HVAC return air ducts
Data centers
Hospitals
Airports

Why CMP is important:

In plenum spaces, air circulation can quickly spread smoke and toxic gases. CMP cables are designed to minimize this risk.

2. OFNP (Optical Fiber Nonconductive Plenum)

OFNP is part of the fiber optic cable classification system under UL standards.

Meaning:

O: Optical fiber
F: Fiber
N: Nonconductive
P: Plenum rated

Key Features:

Designed for fiber optic installations in plenum spaces
Non-metallic (no electrical conductivity)
Very high flame resistance

Typical Applications:

Fiber backbone in plenum areas
High-density data centers
Enterprise network backbone systems

3. LSZH (Low Smoke Zero Halogen)

LSZH (Low Smoke Zero Halogen) is not a UL classification but an international material safety standard widely used in Europe and global projects.

Key Features:

Low smoke emission during fire
No halogen elements (no chlorine, fluorine, bromine)
Reduced toxic gas release
Less corrosive smoke

Typical Applications:

Subway systems
Offshore platforms
Hospitals
Airports
Confined or poorly ventilated areas

How They Are Used Together in Projects

In real engineering projects, these standards are often combined:

CMP copper + LSZH jacket
OFNP fiber + LSZH materials
Full data center cabling with mixed compliance

For example:

A modern data center may use CMP-rated copper cabling for horizontal distribution and OFNP fiber for backboneconnectivity, both with LSZH jackets for enhanced safety.