OFNP

What is OFNP (Optical Fiber Nonconductive Plenum)?

If you have an apartment building, condominium complex, or a co-working space, and you need to wire the building often cabling goes in walls or in the air space above the tile ceilings. Given that it is installed in buildings, one needs to think about the fire, smoke, and shielding of cables. For fiber optic cables, the majority of the cable diameter is not the actual fiber strands, but it is all of the sleeving/shieldings that go around the glass strands.

The concern is that in the event of a fire, the space above the ceiling tile connects the different rooms and is an oxygen-rich environment. We know there are those who run fiber through air ducts, and we are not going to cover that here, but one can imagine the impact of a fire there as well. The NEC restricts the types of materials that can go into these plenum airways to mitigate fire spread.

For new construction, often cable conduits will be installed. This helps protect the cable and can help allow for future expansion. Still, many existing buildings do not have conduits or conduit space to run fiber or other cables. The NEC states that all cabling not in conduit, installed in plenum spaces, shall be listed as having adequate fire-resistant and low smoke-producing characteristics.

As a result, if one runs cable through air-filled spaces (like air ducts, or areas above ceiling tiles that are part of the air distribution system), not through conduit, “plenum” cabling must be used. Plenum cables utilize plastics around the fiber optic strands that utilize flame-retardant, low-smoke materials. These coatings offer both resistance to fire and low smoke if they do burn. Plenum plastics also will not emit large quantities of harmful fumes. The insulation material for optical fiber jumper cables installed in ceiling plenum spaces is called OFNP (Optical Fiber Nonconductive Plenum).

Benefits and Applications of OFNP Cables

OFNP cables have a higher UL-910 fire rating, making them suitable for installation in plenum spaces. The materials used in OFNP cables are designed to be flame-retardant and produce low smoke and toxicity when exposed to fire. This helps to mitigate the risk of fire spread and reduce the potential harm caused by smoke and toxic fumes in the event of a fire. In addition, OFNP cables are non-conductive, as they do not contain any metallic components. This helps to reduce the risk of electrical interference and potential electrical hazards in the building.

Plenum spaces, such as the areas above suspended ceilings or below-raised floors, are used for air circulation in buildings. OFNP cables are specifically designed for installation in these plenum spaces, as they are required to have enhanced fire safety characteristics. OFNP cables are commonly used in a variety of building types, including apartments, condominiums, co-working spaces, and other commercial or residential buildings. They are particularly suitable for communication and data networks, fire alarm systems, and other critical infrastructure within these buildings.

Differences between OFNR and OFNP Cables

The main difference between OFNR (Optical Fiber Nonconductive Riser) and OFNP fiber cables lies in their fire safety ratings and where they can be installed. OFNR cables are designed for use in non-plenum vertical applications such as riser shafts or vertical cable runs between floors. They have limited fire resistance and are not suitable for installation in plenum spaces, which are areas used for air circulation in buildings such as drop ceilings or raised floors. OFNP cables, on the other hand, are specifically designed for use in plenum spaces where fire safety is of utmost importance. Plenum spaces are required to meet stricter fire safety standards due to the potential for fire to spread quickly through air circulation systems. OFNP cables are made with fire-resistant materials and have a higher fire rating than OFNR cables, making them suitable for installation in plenum spaces.