Every building has spaces which are designed to have airflowthrough them. An example of one of these types of spaces includes the area between the ceiling and the dropped ceiling. These areas within buildings are reffered to as "plenum-spaces." The air that circulates through these regions of a building is recirculated through offices and other inhabited regions of the building. To keep cables from running through offices and hallways, it is often convenient to run them through Plenum-spaces instead.

Since there is an abundance of air in these plenum-spaces, they are an extremely effective fuel source for fires. In addition to fires spreading through the building through these spaces, the risk associated with them is worsened by the burning and smoldering of certain types of cables. Most victims of fires die from asphyxiation and blood toxicity due to smoke inhilation. To make matters worse, the standard cable, which is jacketed in PVC, releases two toxic fumes (Hydrochloric Acid and Dioxin) into the air when it burns, and when these smoldering cables are located in plenum-spaces,  toxic fumes can quickly and quietly permeate the entire building. These fumes pose a great danger to anyone within the building including employees and members of the fire department. Due to this danger, code requires Plenum rated cables to be installed through plenum-spaces.

Plenum rated cables are cables that are rated to run through plenum-spaces and are important because their fire-retardant qualities can help save the lives of the people who are inside a building at the time a fire occurs. Fire Test Rating is a CSA certification that is based off of how far a fire will travel along a cable. A Fire Test Rating of 6 (FT6) is the rating that is required by law for plenum-spaces. FT6 burns much slower than other cables and does not release clouds of toxic fumes. It is extremely important that these flammable plenum-spaces are made as safe as possible by using these FT6 rated cables.

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