Fire Safety and Plenum Space: Unraveling the Cable and Uncovering the Facts

The fuel load of certain types of plenum rated cable insulation can rival that of gasoline. In heavily cabled plenums, that’s like placing a gallon of gas within the plenum for every 10 to 30 feet of cable tray (…) Fire retardant jackets on new cables will generally protect against ignition for at least ten minutes of fire exposure, depending on its temperature, (but) worn, heat aged, slit or damaged jacketing that exposes cable insulation to a fire can ignite within minutes.  –Avoiding a Dangerous Journey, by John Michlovic*

Plenum space. If you don’t know how relevant it is, it sounds sort of like something from a Sci-Fi TV show… Deep Plenum Space 9: The Next Frontier. In a lot of ways, it is a new frontier. A misunderstood, mysteriously located space that holds potential for disaster if approached without caution. Plenum is the space in a building that facilitates air circulation, either within a drop ceiling or a raised floor, by providing pathways for airflow. These spaces are outside from Heating Ventilation Air Conditioning (HVAC) systems, which can sometimes become “accidental” plenum spaces due to air ducts that have become loose, misaligned or otherwise compromised by a number of environmental factors or installation-errors.

How does plenum space affect you? Whatever Oxygen is pumping through that space is being forced through the entire building. Which also means if that Oxygen is contaminated by toxic smoke, fumes or flames, those are also being accelerated throughout the building and directly to you.

Let’s talk fire safety. The National Fire Protection Association (NFPA) is an international nonprofit organization formed in 1896 with the purpose of enforcing fire prevention and creating public safety regulations. The NFPA sets the code required for protecting plenum air spaces and the National Electric Code (NEC) is the standard they provide for handling all cables including power, network and video cabling.  Today, the NFPA holds about 300 safety codes and standards. Due to these regulations and standards, a variety of testing certifications have been implemented, including the Underwriters Laboratory (UL) Standards as well as ETL Listings, which I’ll explain further down the page. Safety investigations and testing through UL Certification and ETL Listing processes are recognized as “the standard,” and therefore recommended for optimal-safety use.

Fire safety is an obvious top priority when implementing any type of electronics or cabling system into building construction, for a number of reasons. Many new and refurbished buildings use plenum spaces to house a variety of cabling, plumbing, and similar mechanical and electrical services. Because this space is used to push airflow throughout the building, in the event of an electrical fire the smoke and flames would be pushed throughout the entire building at a rapid rate. This is why it’s so important to always use products and cabling that are certified as Plenum-rated, even in temporary applications. Plenum-rated cables minimize the risk for flames, smoke or fumes to blow through the plenum space by using jackets treated with a polymer material that are designed to hinder the progression of potential flames as well as not release any sort of harmful smoke that normally accompanies any type of burning plastic.

Another fire safety concern in plenum spaces is the potential for circulation of poisonous gases and fumes from burning plastics. Most forms of plastic burns quickly, giving off a thick cloud of black toxic smoke. According to the NFPA:

“Most fire deaths are not caused by burns, but by smoke inhalation. The synthetic materials commonplace in today’s homes produce especially dangerous substances. As a fire grows inside a building, it will often consume most of the available oxygen, slowing the burning process. This ‘incomplete combustion’ results in toxic gases.”**

This means that proper cabling materials are pivotal in fire protection and safety, especially as installers seek cost-reducing materials that may be new to the market and therefore minimally tested for safety precautions. It’s important to keep up-to-date with safety standards by using materials that comply with NFPA regulations and come with UL Certification or an ETL Listing.  UL 2043 Classification compliance means that the product has been fire-tested using open flame ignition source to determine safety-regulated fire performance and smoke characteristics. Just like UL Listings, ETL listings are recognized by OHSHA as a Nationally Recognized Testing Laboratory. Products such as our GB-AVSTOR3 False Ceiling Equipment Storage Unit are among the many solutions we’ve tested to meet UL-Classification and/or ETL Listing standards. This ensures not only functionality but also precautionary safety. For more information on any of our UL-Certified and ETL-Listed products, contact us at (800) 368-9700.

*Michlovic, John. “Avoiding a Dangerous Journey.” HH Robertson, In-Floor Cable Distribution Systems. Web. 6 May 2014.
** “The Consequences of Fire, from A Reporters Guide to Fire and the NFPA.” Web. 6 May 014.