Fiber optic cable OFNR flame retardant rating

Fiber optic cables are typically made with PVC, PE, or LSZH jackets, with flame retardant ratings such as OFNP (Plenum), OFNR (Riser), and OFNG (General Purpose) determining their fire safety and installation suitability.

Common Fiber Optic Cable Materials

• PVC (Polyvinyl Chloride): Widely used for indoor applications, PVC is flexible and cost-effective but emits toxic halogen gases when burned. Flame-retardant PVC (FR-PVC) exists but is less common due to halogen concerns .
• PE (Polyethylene): Offers good mechanical strength and moisture resistance, often used outdoors. Standard PE is not inherently flame-retardant .
• LSZH (Low Smoke Zero Halogen): LSZH jackets are formulated without halogens, producing minimal smoke and no corrosive gases when burned. This makes LSZH ideal for confined or poorly ventilated spaces such as hospitals, airports, tunnels, and data centers . LSZH cables are generally stiffer and more expensive than PVC.

Flame Retardant Ratings

Fiber optic cables are classified according to fire safety standards, primarily defined by the National Electrical Code (NEC):

• OFNP (Optical Fiber Non-conductive Plenum): Highest fire resistance, suitable for plenum spaces like air ducts and ceiling voids. Produces low smoke and minimal toxic gases .
• OFNR (Optical Fiber Non-conductive Riser): Designed for vertical riser shafts between floors. Lower fire resistance than OFNP and cannot be used in plenum areas .
• OFNG (Optical Fiber Non-conductive General Purpose): Suitable for general-purpose areas with minimal fire resistance requirements . Key points about flame retardancy:
• Flame-retardant materials slow fire spread and tend to self-extinguish once the flame source is removed; they do not make the cable completely non-flammable .
• LSZH is preferred in Europe and the U.S. for safety-critical installations due to its low smoke and halogen-free properties .
• Fire ratings also consider smoke density, halogen-acid emissions, and compliance with building codes .

Choosing the Right Cable

When selecting a fiber optic cable, consider:

1. Installation environment: Plenum, riser, or general-purpose areas.
2. Fire safety requirements: Compliance with NEC or local building codes.
3. Material properties: Flexibility, cost, smoke emission, and halogen content. For example, OFNP LSZH cables are ideal for indoor plenum spaces, while OFNR PVC cables may suffice for vertical risers in commercial buildings. Outdoor installations often use PE jackets for durability and weather resistance . By matching the cable material and flame retardant rating to the installation environment, you ensure both safety and performance of the fiber optic network.