What is the difference between riser and plenum rated Ethernet cables?

Riser rated (CMR) cable is PVC. Riser rated cable is suitable for use inside walls and runs vertically between floors. Typically, the fire resistance is due to a Teflon coating on the cable or strands of fibers baked into the jacket that limit the ability of the cable to carry a flame. If the cable should burn, the resultant smoke and fumes are toxic. Riser rated cable is the most common jacket type found on the market and is much lower in cost. Riser rated cable may be used in any part of your structure EXCEPT the Plenum.

Inside a commercial building (this can mean office, school, hotel, motel, and more) the construction contractor installed a HVAC system inside the Plenum. The Plenum area is a likely spot for installing cabling. As convenient as this is, it brings special considerations related to fire and toxic smoke.

The Plenum area is a great way to channel a fire and resultant smoke from one spot to the next in a building, and quickly.
PVC cable, without a Plenum rating, will aid in spreading a fire and the resultant highly toxic smoke will end up invading the common living/working spaces which will cause anything from immediate fatality to long term health issues.

Given the critical nature of fire protection, a Plenum cable cable performance rating was established. Commonly, Plenum cable is constructed from FEP (fluorinated ethylene propylene). FEP is essentially a plasticized Teflon. FEP emits little smoke when burning and is low toxicity.

Plenum cable is more expensive than non-Plenum cable. Ultimately, the decision won’t be the installers to make. Local fire codes, insurance requirements, or even customer requirements will dictate if Plenum must be used. Regardless, NEVER use plain PVC cable in a Plenum space. Plenum rated cable can be installed in all spaces but the per-foot cost involved typically prohibits this.

To learn more about Ethernet cable jacket types, check out our Cable Academy blogs below!

What is the difference between riser and plenum rated Ethernet cables?Updated 9 months ago