Choosing the Right Low-Voltage Cable to Preserve Fire Safety
Fire safety standard compliance is just as important as performance ratings, shielding composition, conductor size and product warranties.
Image courtesy of Kordz
It’s easy to get mired in the specs when addressing the topic of low-voltage cabling.
Certainly, performance ratings, shielding composition, conductor size and product warranties are all important considerations. Still, there’s one very critical aspect that bears just as much weight: compliance with fire safety standards.
In the unfortunate event of a fire, if a cable you installed is found responsible and does not comply with regulatory fire safety standards, you and your company are liable for damages due to negligence.
To protect your professional reputation, the legal and financial health of your business, and most importantly, human life, it’s paramount to understand cable fire ratings and apply this knowledge to the selection and installation of low-voltage cabling.
Here are some valuable information and tips to ensure that you’re up to code (noting please, requirements may vary by county and state):
Types of Fire-Rated Cable
The United States National Fire Protection Agency (NFPA) National Electrical Code stipulates best practices and safety requirements for all parts of a residential or commercial building where cable may reside. These areas include Plenum, Riser, General Purpose and [residential] Dwelling.
Measurements of a cable’s performance under controlled testing environments determine its classification. For example, cables that satisfy the most stringent fire safety requirements are rated with suffix ‘P’, which stands for Plenum.
Plenum rated cables provide a higher degree of fire resistance and emit less smoke than other types of cables. This prevents smoke from burning cables being sucked into and spread throughout a home or building via HVAC ducts, which are the most common type of plenum spaces.
Photo courtesy of Kordz
Do Fire Ratings Apply to HDMI?
There’s some confusion about whether or not pre-terminated cable, such as an HDMI cable or a pre-terminated network patch cord, needs to satisfy fire-rating requirements. The general answer is no, but only if the cable is installed in a non-permanent manner.
Pre-terminated cables that can be easily removed without significant damage to the structure of a home or building are difficult to classify as ‘construction products’; therefore, they are not bound by the requirements of building safety codes.
However, if the HDMI cable is installed permanently and is inaccessible, it’s best to err on the side of caution and attempt compliance with local regulations. Look out for certification labeling on the packaging of HDMI cable of UL444 CMG or UL13 CL3.
Fire Rating Measurements
The chemical composition of a cable’s jacket and filler impact upon how it reacts to fire. Typical variables measured include flame propagation, heat release, smoke release, acidity of released substances and production of droplets.
Flame propagation, or flame spread, is the conductance of heat along a cable. The longer the propagation of flame, the more likely the cable will be responsible for moving fire from one room to the next.
Fire can also be spread when the burning source radiates sufficient heat to surrounding materials to ignite it. Aside from the amount of oxygen and fuel available in a burning environment, the calorific value of a cable can contribute to heat release.
The lower a cable’s calorific value, (MJ/kg), the better it is at controlling the release of heat.
The inhalation of smoke is often the true cause of death in a fire. Common measurements of smoke generation are optical density, indicated as opacity, and smoke release rate in square meters per second.
Other measurements, typically used in European fire rating standards, are the amount of toxic substance released into the air and the degree of flame spread caused by melted cable droplets.
Photo courtesy of Kordz
Five Steps to Ensure Compliance of Fire Safety Regulations
Understand Your Responsibilities: As the specifying systems integrator of the cabling and other components of an installation, you bear a responsibility to ensure that the building into which technology is installed, is safe for inhabitants.
Identify the Certification or Compliance Relevant to Your Region: Read up and determine which fire rating standards and certifications are relevant before moving ahead on a project. This is particularly important if you have customers throughout the country. Have copies of regulations and best practice guidance documents on hand.
Choose Products That Comply with the Required Fire Rating: Assess and control the risks associated with fire by specifying the correct cabling in adherence with the local safety regulations and best practices. Look for the relevant certification and compliance marks on packaging and question your suppliers to ensure the products deliver on their claims.
Obtain Proof of Compliance: Always ask your cable supplier for proof of compliance. Unfortunately, a product claiming to satisfy a particular fire rating standard may not actually be compliant at all, since it’s quite easy to print anything on the product packaging.
Manufacturers are required to provide documented evidence of fire-rating compliance, either directly on their website or upon request, whether in the form of certification from third-party regulatory bodies, such as UL LLC in the U.S.A., or in the form of test reports.
Systems integrators are usually the contractors on a project who install low-voltage cabling, making them ultimately liable for using non-compliant products, unless they can demonstrate all possible efforts were made to ensure compliance.
Keep Records: Finally, file and back up compliance documents in a safe place as evidence in case of future liability.
While low-voltage cable rarely starts a fire, it can easily spread it. It’s up to you to specify and install the right type of fire-rated cable to stay up to code and to protect yourself and your customers. By understanding how cable is tested and categorized, you can specify and install it with confidence.
Substitutions—Are They Allowed?
Low-voltage cable, including fire alarm, audio, Ethernet, security and access control cable, is tested for fire safety performance in three primary environments found in residential and commercial environments: plenum, riser and general purpose.
In some cases, it’s okay per code to substitute one type of cable for another. It’s often better for the budget to do so, after all. However, caution is advised. If you make an inappropriate substitution, you could be heading for trouble. Here’s a guide to ensure you’re always to code:
- Because plenum-rated cables meet the highest fire-resistance standards of all categories, they can be installed in place of riser or general purpose cable.
- Riser cable is the second most fire-resistant. It can be used in general purpose areas, but not in plenums.
- The least fire-resistant of all is general purpose, which means it should not be substituted for riser or plenum cable.
- Another important distinction is flame retardant versus flame resistant. A flame retardant cable slows down but doesn’t stop the propagation of a flame. A flame resistant cable, on the other hand, continues to operate under high temperatures or under a direct flame. This type of cable is most commonly used in security and industrial applications; for example, when a cable must continue to work in a burning building for a fire safety door to remain open. These circuit integrity cables continue to operate in the presence of a fire and are sometimes called 1-hour or 2-hour fire-rated cables. The differences between these two ratings are essential for the critical circuits required for life safety requirements.
Did you know that the number one cause of fire in the U.S. is unattended cooking? Low-voltage cabling is unlikely to cause a fire, however it can be a significant factor in the creation of smoke, which impedes escape, or worse creates toxic smoke, both of which put human life in jeopardy.
Make sure you’re doing your part and get it right by making informed choices.
James Chen is the managing director of Kordz International and Hugo Fitzjohn is the Kordz technical author.
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