A Brief Introduction Of Fiber Optic Patch Cable Fire & Smoking Ratings

When talking about fiber optic cable (here we mainly refer to the fiber patch cables), there are many kinds of fiber patch cable according to different classifications. For example, according to the fiber cable mode, there are singlemode fiber patch cable and multimode fiber patch cable while according to fiber cable structure, there are simplex fiber optic patch cable and duplex fiber patch cable. Of cause, the most common calssification is according to the connector types of the cables, such as the familiar SC fiber patch cord, LC-LC fiber patch cord etc.

 

However, today, we will not repeat these knowledge, but want to introduce the fiber patch cable from another perspective. As we know, according to NEC (National Electrical Code), a building's inside area is divided into three types of sections: plenums, risers and general purpose areas, thus there are specific standard fiber optic patch cable that are designed to used in those specific areas. The most common used fiber patch cables in plenums and risers are OFNP Cables and OFNR cables. In addition, according to different fiber optic cable fire ratings, there are also OFCP cables, OFCR cables, OFNG cables and OFCG cables.

 

First, we give a definition to these three types of sections of a building's inside area.


Building's Inside Area

Plemun Area A Plenum area is refered to a building space used for air flow or air distribution system. Generally, in most buildings, the area above a drop ceiling or under a raised floor is used as the air return (source of air) for the air conditioning. And fiber cables are often installed in those drop ceiling and raised floors. If the cables were burning, and giving off toxic fumes and the fumes, the rest of the building would be fed with fumes through the air conditioner. As a result, people could also be dangerous even though they are a long way from the fire.

 

Riser Area Compared to the plenum area, riser area is more easy to understand. A riser area is usually refered to a floor opening, shaft or duct that runs vertically through one or more floors.

 

General Purpose Area General purpose area consist of all the area except the plenum or and riser area and on the same floor.

 

A Brief Introduction Of Fiber Optic Patch Cable Fire & Smoking Ratings We may be familiar with the words, such as OFNP, OFNR, OFCP etc., but we may not really know what are the meaning of them. They refers the UL level, ie. UL fire rating. UL means Underwriters Laboratories which is the largest and best knownindependent, not-for-profit testing laboratory in the world. UL fire rating is generally divided into different levels from high to low:
  • Booster Level -CMP copper, OFNP and OFCP( Air combustion test / Tolstoy sodium duct experiments plenum flame test / Steiner tunnel test)
  • Riser Stage -CMR copper, OFNR and OFCR ( Vertical burning test / Riser flame test)
  • Commercial Level -CM copper, OFN and OFC ( Vertical burning test / Vertial tray flame test)
  • General Purpose -CMG copper, OFNG and OFCG ( Vertical burning test / Vertial tray flame test)
  • Household Level – CMX copper( Vertical burning test / Vertial wire flame test)
Booster Level including CMP copper (UTP and ScTP) cables as well as OFNP or OFCP fiber optic cable, is cables of highest level.

 

OFNP Cables OFNP stands for Optical Fiber Nonconductive Plenum. OFNP cables have fire-resistance and low smoke production characteristics. They can be installed in ducts, plenums and other spaces used for building airflow. This is the highest fire rating fiber cable and no other cable types can be used as substitutes.

 

OFCP Cables OFCP stands for Optical Fiber Conductive Plenum. OFCP cables have the same fire and smoking rating as OFNP cables but they have a conducting armor or central strength member which is usually steel. OFCP cables must be properly grounded at both ends. As a result, OFCP cables can not be installed in the same cable tray or conduit as power cables.

 

Riser Stage including the CMR copper cables and OFNR or OFCR fiber optic cables, is the second highest level cables.

 

OFNR Cables OFNR stands for Optical Fiber Nonconductive Riser. OFNR cables are used in Riser areas which are building vertical shafts or runs from one floor to another floor. OFNR cables can not be installed in plenum areas since they do not have the required fire and smoking rating as Plenum rated cables. OFNP plenum cables can be used as substitutes for OFNR cables.

 

OFCR Cables OFCR stands for Optical Fiber Conductive Riser. OFCR cables have the same fire rating characteristics as OFNR cables but they have conducting armor or central strength member which is usually steel. OFCR cables should also be properly grounded at both ends. OFCP cables can be used as substitutes for OFCR cables. OFCR cables can not be installed in the same cable trays or conduits as power cables.

 

General Purpose including CMG copper cable and OFNG or OFCG fiber optic cable, is for commercial use.

 

OFNG Cables OFNG stands for Optical Fiber Nonconductive General-Purpose. They are typically used in horizontal cabling, single floor applications. OFNG cables can not be used in plenums or risers. OFNP and OFNR cables both can be used as substitutes for OFNG cables.

 

OFCG Cables OFCG stands for Optical Fiber Conductive General-Purpose. They have the same fire characteristics as OFNG cables but they have conducting armor or central strength members which is typically steel. OFCG cables should be properly grounded at both ends. They should not be installed in the same cable tray or conduits as power cables.

 

In addition, the cables of commercial level including the CM copper cable, OFN and OFC fiber optic cables is similar with the general purpose cables. And the household level usually includes the CMX copper but generally not includes the fiber optic cables that is the lowest level of UL fire ratings. However, for more safety, LSZH cables (LSZH means low-smoke, zero-halogen. LSZH cable in principle is to let the flame does not produce a lot of gas and smoke when burned, so that people will not burn a lot of harm caused , greatly improving the survival rate of people in the fire.) are gradually widely used in indoor cable installation.

 

Warm Tips: Although the NEC may allow non-plenum cable, the final decision is up to your local Fire Marshall. Most cities adopt the national codes as their own without revision, but some cities modify or expand them and require plenum-rated cable in all situations. Regardless of the code or its interpretation, your Fire Marshall makes the final decision. We recommend that you contact your Fire Marshall if you have questions. If you have any requirements of the related products of this article, welcome to visit the official website of Fiberstore.