If you’re looking into replacing or repairing sections of your fire alarm system, one of the most fundamental concepts to understand are the two fire safety classifications for a Fire Alarm Cable. What many people don’t know is that the type of cable chosen for different sections of your fire alarm system can not only be a matter of safety but legality as well. Fire safety codes designed by the National Fire Protection Association (NFPA) lay out two categorizations for fire alarm cables. This blog will explain each type and give you a basic understanding of where each type should be used.
Type 1: Plenum Cable
Plenum cable is designed for use in “plenum space,” which is any non-living/working section of a building between floors that allows for airflow from cooling and heating systems. Some examples of plenum space are ducts or vents, open space above ceiling panels, and open areas around heat and cooling system air intakes in non-working/living spaces. Plenum spaces are considered a higher risk area for cables in the case of a fire, and as a result, the NFPA has ruled that special types of cable must be used in these places. NFPA rules on plenum-rated cable were designed both to prevent fires and to prevent the failure of fire alarm systems in the case of a fire.
Plenum space is considered particularly risky primarily because of the fact that in the case of fire, heat and cooling systems will continually bring oxygen to flames that reach plenum space. Additionally, however, plenum space is considered dangerous because it is generally out of sight of those who may be working or living in the building.
If you’re rewiring sections of your fire alarm system and you are not sure if a space is plenum space or not, err on the side of caution and purchase plenum rated cables. Significant risk of non-plenum space unintentionally becoming plenum space has been noted by major fire safety authorities. Something as simple as a duct seal being breached can make non-plenum space take on the hazardous qualities of plenum space as a result of the introduction of oxygen flow. As a result, when in doubt, choose plenum rated fire alarm cable.
Type 2: Riser Cable
Riser cable is, predictably, cable that is designed for non-plenum areas between floors. This rating denotes cables that have flame-retardant insulation but not to the degree of plenum rated cables. As mentioned above, while plenum cable is perfectly viable for use in non-plenum spaces, it is not recommended to choose riser rated cable in areas that could be or could potentially become plenum space.
Riser cables are ideal for areas that are far removed from air circulation vents, well-sealed from other areas, and confirmed not to have fresh air circulation.
When buying fire alarm cables, regardless of rating, you should be aware that the special insulation used can severely reduce the flexibility of the cables. As a result, plan to run cables longer and with more leeway than you might usually expect. Overly flexing a plenum or riser rated cable can result in fire alarm cables that are split, cracked, or damaged internally. Understandably, this is a severe risk in the case that a fire does occur.
If you have further questions about alarm cables, our staff can help. Our store carries certified alarm cables of multiple types, both plenum rated and riser rated, and we are well-educated on their application. Come check out our store and find the information you need today at www.ewcswire.com!